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freebsd-skq/sys/dev/xen/blkback/blkback.c
gibbs 14b10376c4 sys/dev/xen/blkback/blkback.c: 
In xbb_detach() only perform cleanup of our taskqueue and
	device statistics structures if they have been initialized.
	This avoids a panic when xbb_detach() is called on a partially
	initialized device instance, due to an early failure in
	attach.

Sponsored by:	Spectra Logic Corporation
2010-10-28 04:14:28 +00:00

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/*-
* Copyright (c) 2009-2010 Spectra Logic Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* substantially similar to the "NO WARRANTY" disclaimer below
* ("Disclaimer") and any redistribution must be conditioned upon
* including a substantially similar Disclaimer requirement for further
* binary redistribution.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*
* Authors: Justin T. Gibbs (Spectra Logic Corporation)
* Ken Merry (Spectra Logic Corporation)
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/**
* \file blkback.c
*
* \brief Device driver supporting the vending of block storage from
* a FreeBSD domain to other domains.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/bio.h>
#include <sys/bus.h>
#include <sys/conf.h>
#include <sys/devicestat.h>
#include <sys/disk.h>
#include <sys/fcntl.h>
#include <sys/filedesc.h>
#include <sys/kdb.h>
#include <sys/module.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/rman.h>
#include <sys/taskqueue.h>
#include <sys/types.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <geom/geom.h>
#include <machine/_inttypes.h>
#include <machine/xen/xen-os.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <xen/blkif.h>
#include <xen/evtchn.h>
#include <xen/gnttab.h>
#include <xen/xen_intr.h>
#include <xen/interface/event_channel.h>
#include <xen/interface/grant_table.h>
#include <xen/xenbus/xenbusvar.h>
/*--------------------------- Compile-time Tunables --------------------------*/
/**
* The maximum number of outstanding request blocks (request headers plus
* additional segment blocks) we will allow in a negotiated block-front/back
* communication channel.
*/
#define XBB_MAX_REQUESTS 256
/**
* \brief Define to force all I/O to be performed on memory owned by the
* backend device, with a copy-in/out to the remote domain's memory.
*
* \note This option is currently required when this driver's domain is
* operating in HVM mode on a system using an IOMMU.
*
* This driver uses Xen's grant table API to gain access to the memory of
* the remote domains it serves. When our domain is operating in PV mode,
* the grant table mechanism directly updates our domain's page table entries
* to point to the physical pages of the remote domain. This scheme guarantees
* that blkback and the backing devices it uses can safely perform DMA
* operations to satisfy requests. In HVM mode, Xen may use a HW IOMMU to
* insure that our domain cannot DMA to pages owned by another domain. As
* of Xen 4.0, IOMMU mappings for HVM guests are not updated via the grant
* table API. For this reason, in HVM mode, we must bounce all requests into
* memory that is mapped into our domain at domain startup and thus has
* valid IOMMU mappings.
*/
#define XBB_USE_BOUNCE_BUFFERS
/**
* \brief Define to enable rudimentary request logging to the console.
*/
#undef XBB_DEBUG
/*---------------------------------- Macros ----------------------------------*/
/**
* Custom malloc type for all driver allocations.
*/
MALLOC_DEFINE(M_XENBLOCKBACK, "xbbd", "Xen Block Back Driver Data");
#ifdef XBB_DEBUG
#define DPRINTF(fmt, args...) \
printf("xbb(%s:%d): " fmt, __FUNCTION__, __LINE__, ##args)
#else
#define DPRINTF(fmt, args...) do {} while(0)
#endif
/**
* The maximum mapped region size per request we will allow in a negotiated
* block-front/back communication channel.
*/
#define XBB_MAX_REQUEST_SIZE \
MIN(MAXPHYS, BLKIF_MAX_SEGMENTS_PER_REQUEST * PAGE_SIZE)
/**
* The maximum number of segments (within a request header and accompanying
* segment blocks) per request we will allow in a negotiated block-front/back
* communication channel.
*/
#define XBB_MAX_SEGMENTS_PER_REQUEST \
(MIN(UIO_MAXIOV, \
MIN(BLKIF_MAX_SEGMENTS_PER_REQUEST, \
(XBB_MAX_REQUEST_SIZE / PAGE_SIZE) + 1)))
/**
* The maximum number of shared memory ring pages we will allow in a
* negotiated block-front/back communication channel. Allow enough
* ring space for all requests to be XBB_MAX_REQUEST_SIZE'd.
*/
#define XBB_MAX_RING_PAGES \
BLKIF_RING_PAGES(BLKIF_SEGS_TO_BLOCKS(XBB_MAX_SEGMENTS_PER_REQUEST) \
* XBB_MAX_REQUESTS)
/*--------------------------- Forward Declarations ---------------------------*/
struct xbb_softc;
static void xbb_attach_failed(struct xbb_softc *xbb, int err, const char *fmt,
...) __attribute__((format(printf, 3, 4)));
static int xbb_shutdown(struct xbb_softc *xbb);
static int xbb_detach(device_t dev);
/*------------------------------ Data Structures -----------------------------*/
/**
* \brief Object tracking an in-flight I/O from a Xen VBD consumer.
*/
struct xbb_xen_req {
/**
* Linked list links used to aggregate idle request in the
* request free pool (xbb->request_free_slist).
*/
SLIST_ENTRY(xbb_xen_req) links;
/**
* Back reference to the parent block back instance for this
* request. Used during bio_done handling.
*/
struct xbb_softc *xbb;
/**
* The remote domain's identifier for this I/O request.
*/
uint64_t id;
/**
* Kernel virtual address space reserved for this request
* structure and used to map the remote domain's pages for
* this I/O, into our domain's address space.
*/
uint8_t *kva;
#ifdef XBB_USE_BOUNCE_BUFFERS
/**
* Pre-allocated domain local memory used to proxy remote
* domain memory during I/O operations.
*/
uint8_t *bounce;
#endif
/**
* Base, psuedo-physical address, corresponding to the start
* of this request's kva region.
*/
uint64_t gnt_base;
/**
* The number of pages currently mapped for this request.
*/
int nr_pages;
/**
* The number of 512 byte sectors comprising this requests.
*/
int nr_512b_sectors;
/**
* The number of struct bio requests still outstanding for this
* request on the backend device. This field is only used for
* device (rather than file) backed I/O.
*/
int pendcnt;
/**
* BLKIF_OP code for this request.
*/
int operation;
/**
* BLKIF_RSP status code for this request.
*
* This field allows an error status to be recorded even if the
* delivery of this status must be deferred. Deferred reporting
* is necessary, for example, when an error is detected during
* completion processing of one bio when other bios for this
* request are still outstanding.
*/
int status;
/**
* Device statistics request ordering type (ordered or simple).
*/
devstat_tag_type ds_tag_type;
/**
* Device statistics request type (read, write, no_data).
*/
devstat_trans_flags ds_trans_type;
/**
* The start time for this request.
*/
struct bintime ds_t0;
/**
* Array of grant handles (one per page) used to map this request.
*/
grant_handle_t *gnt_handles;
};
SLIST_HEAD(xbb_xen_req_slist, xbb_xen_req);
/**
* \brief Configuration data for the shared memory request ring
* used to communicate with the front-end client of this
* this driver.
*/
struct xbb_ring_config {
/** KVA address where ring memory is mapped. */
vm_offset_t va;
/** The pseudo-physical address where ring memory is mapped.*/
uint64_t gnt_addr;
/**
* Grant table handles, one per-ring page, returned by the
* hyperpervisor upon mapping of the ring and required to
* unmap it when a connection is torn down.
*/
grant_handle_t handle[XBB_MAX_RING_PAGES];
/**
* The device bus address returned by the hypervisor when
* mapping the ring and required to unmap it when a connection
* is torn down.
*/
uint64_t bus_addr[XBB_MAX_RING_PAGES];
/** The number of ring pages mapped for the current connection. */
u_int ring_pages;
/**
* The grant references, one per-ring page, supplied by the
* front-end, allowing us to reference the ring pages in the
* front-end's domain and to map these pages into our own domain.
*/
grant_ref_t ring_ref[XBB_MAX_RING_PAGES];
/** The interrupt driven even channel used to signal ring events. */
evtchn_port_t evtchn;
};
/**
* Per-instance connection state flags.
*/
typedef enum
{
/**
* The front-end requested a read-only mount of the
* back-end device/file.
*/
XBBF_READ_ONLY = 0x01,
/** Communication with the front-end has been established. */
XBBF_RING_CONNECTED = 0x02,
/**
* Front-end requests exist in the ring and are waiting for
* xbb_xen_req objects to free up.
*/
XBBF_RESOURCE_SHORTAGE = 0x04,
/** Connection teardown in progress. */
XBBF_SHUTDOWN = 0x08
} xbb_flag_t;
/** Backend device type. */
typedef enum {
/** Backend type unknown. */
XBB_TYPE_NONE = 0x00,
/**
* Backend type disk (access via cdev switch
* strategy routine).
*/
XBB_TYPE_DISK = 0x01,
/** Backend type file (access vnode operations.). */
XBB_TYPE_FILE = 0x02
} xbb_type;
/**
* \brief Structure used to memoize information about a per-request
* scatter-gather list.
*
* The chief benefit of using this data structure is it avoids having
* to reparse the possibly discontiguous S/G list in the original
* request. Due to the way that the mapping of the memory backing an
* I/O transaction is handled by Xen, a second pass is unavoidable.
* At least this way the second walk is a simple array traversal.
*
* \note A single Scatter/Gather element in the block interface covers
* at most 1 machine page. In this context a sector (blkif
* nomenclature, not what I'd choose) is a 512b aligned unit
* of mapping within the machine page referenced by an S/G
* element.
*/
struct xbb_sg {
/** The number of 512b data chunks mapped in this S/G element. */
int16_t nsect;
/**
* The index (0 based) of the first 512b data chunk mapped
* in this S/G element.
*/
uint8_t first_sect;
/**
* The index (0 based) of the last 512b data chunk mapped
* in this S/G element.
*/
uint8_t last_sect;
};
/**
* Character device backend specific configuration data.
*/
struct xbb_dev_data {
/** Cdev used for device backend access. */
struct cdev *cdev;
/** Cdev switch used for device backend access. */
struct cdevsw *csw;
/** Used to hold a reference on opened cdev backend devices. */
int dev_ref;
};
/**
* File backend specific configuration data.
*/
struct xbb_file_data {
/** Credentials to use for vnode backed (file based) I/O. */
struct ucred *cred;
/**
* \brief Array of io vectors used to process file based I/O.
*
* Only a single file based request is outstanding per-xbb instance,
* so we only need one of these.
*/
struct iovec xiovecs[XBB_MAX_SEGMENTS_PER_REQUEST];
#ifdef XBB_USE_BOUNCE_BUFFERS
/**
* \brief Array of io vectors used to handle bouncing of file reads.
*
* Vnode operations are free to modify uio data during their
* exectuion. In the case of a read with bounce buffering active,
* we need some of the data from the original uio in order to
* bounce-out the read data. This array serves as the temporary
* storage for this saved data.
*/
struct iovec saved_xiovecs[XBB_MAX_SEGMENTS_PER_REQUEST];
/**
* \brief Array of memoized bounce buffer kva offsets used
* in the file based backend.
*
* Due to the way that the mapping of the memory backing an
* I/O transaction is handled by Xen, a second pass through
* the request sg elements is unavoidable. We memoize the computed
* bounce address here to reduce the cost of the second walk.
*/
void *xiovecs_vaddr[XBB_MAX_SEGMENTS_PER_REQUEST];
#endif /* XBB_USE_BOUNCE_BUFFERS */
};
/**
* Collection of backend type specific data.
*/
union xbb_backend_data {
struct xbb_dev_data dev;
struct xbb_file_data file;
};
/**
* Function signature of backend specific I/O handlers.
*/
typedef int (*xbb_dispatch_t)(struct xbb_softc *xbb, blkif_request_t *ring_req,
struct xbb_xen_req *req, int nseg,
int operation, int flags);
/**
* Per-instance configuration data.
*/
struct xbb_softc {
/**
* Task-queue used to process I/O requests.
*/
struct taskqueue *io_taskqueue;
/**
* Single "run the request queue" task enqueued
* on io_taskqueue.
*/
struct task io_task;
/** Device type for this instance. */
xbb_type device_type;
/** NewBus device corresponding to this instance. */
device_t dev;
/** Backend specific dispatch routine for this instance. */
xbb_dispatch_t dispatch_io;
/** The number of requests outstanding on the backend device/file. */
u_int active_request_count;
/** Free pool of request tracking structures. */
struct xbb_xen_req_slist request_free_slist;
/** Array, sized at connection time, of request tracking structures. */
struct xbb_xen_req *requests;
/**
* Global pool of kva used for mapping remote domain ring
* and I/O transaction data.
*/
vm_offset_t kva;
/** Psuedo-physical address corresponding to kva. */
uint64_t gnt_base_addr;
/** The size of the global kva pool. */
int kva_size;
/**
* \brief Cached value of the front-end's domain id.
*
* This value is used at once for each mapped page in
* a transaction. We cache it to avoid incuring the
* cost of an ivar access every time this is needed.
*/
domid_t otherend_id;
/**
* \brief The blkif protocol abi in effect.
*
* There are situations where the back and front ends can
* have a different, native abi (e.g. intel x86_64 and
* 32bit x86 domains on the same machine). The back-end
* always accomodates the front-end's native abi. That
* value is pulled from the XenStore and recorded here.
*/
int abi;
/**
* \brief The maximum number of requests allowed to be in
* flight at a time.
*
* This value is negotiated via the XenStore.
*/
uint32_t max_requests;
/**
* \brief The maximum number of segments (1 page per segment)
* that can be mapped by a request.
*
* This value is negotiated via the XenStore.
*/
uint32_t max_request_segments;
/**
* The maximum size of any request to this back-end
* device.
*
* This value is negotiated via the XenStore.
*/
uint32_t max_request_size;
/** Various configuration and state bit flags. */
xbb_flag_t flags;
/** Ring mapping and interrupt configuration data. */
struct xbb_ring_config ring_config;
/** Runtime, cross-abi safe, structures for ring access. */
blkif_back_rings_t rings;
/** IRQ mapping for the communication ring event channel. */
int irq;
/**
* \brief Backend access mode flags (e.g. write, or read-only).
*
* This value is passed to us by the front-end via the XenStore.
*/
char *dev_mode;
/**
* \brief Backend device type (e.g. "disk", "cdrom", "floppy").
*
* This value is passed to us by the front-end via the XenStore.
* Currently unused.
*/
char *dev_type;
/**
* \brief Backend device/file identifier.
*
* This value is passed to us by the front-end via the XenStore.
* We expect this to be a POSIX path indicating the file or
* device to open.
*/
char *dev_name;
/**
* Vnode corresponding to the backend device node or file
* we are acessing.
*/
struct vnode *vn;
union xbb_backend_data backend;
/** The native sector size of the backend. */
u_int sector_size;
/** log2 of sector_size. */
u_int sector_size_shift;
/** Size in bytes of the backend device or file. */
off_t media_size;
/**
* \brief media_size expressed in terms of the backend native
* sector size.
*
* (e.g. xbb->media_size >> xbb->sector_size_shift).
*/
uint64_t media_num_sectors;
/**
* \brief Array of memoized scatter gather data computed during the
* conversion of blkif ring requests to internal xbb_xen_req
* structures.
*
* Ring processing is serialized so we only need one of these.
*/
struct xbb_sg xbb_sgs[XBB_MAX_SEGMENTS_PER_REQUEST];
/** Mutex protecting per-instance data. */
struct mtx lock;
#ifdef XENHVM
/**
* Resource representing allocated physical address space
* associated with our per-instance kva region.
*/
struct resource *pseudo_phys_res;
/** Resource id for allocated physical address space. */
int pseudo_phys_res_id;
#endif
/** I/O statistics. */
struct devstat *xbb_stats;
};
/*---------------------------- Request Processing ----------------------------*/
/**
* Allocate an internal transaction tracking structure from the free pool.
*
* \param xbb Per-instance xbb configuration structure.
*
* \return On success, a pointer to the allocated xbb_xen_req structure.
* Otherwise NULL.
*/
static inline struct xbb_xen_req *
xbb_get_req(struct xbb_softc *xbb)
{
struct xbb_xen_req *req;
req = NULL;
mtx_lock(&xbb->lock);
/*
* Do not allow new requests to be allocated while we
* are shutting down.
*/
if ((xbb->flags & XBBF_SHUTDOWN) == 0) {
if ((req = SLIST_FIRST(&xbb->request_free_slist)) != NULL) {
SLIST_REMOVE_HEAD(&xbb->request_free_slist, links);
xbb->active_request_count++;
} else {
xbb->flags |= XBBF_RESOURCE_SHORTAGE;
}
}
mtx_unlock(&xbb->lock);
return (req);
}
/**
* Return an allocated transaction tracking structure to the free pool.
*
* \param xbb Per-instance xbb configuration structure.
* \param req The request structure to free.
*/
static inline void
xbb_release_req(struct xbb_softc *xbb, struct xbb_xen_req *req)
{
int wake_thread;
mtx_lock(&xbb->lock);
wake_thread = xbb->flags & XBBF_RESOURCE_SHORTAGE;
xbb->flags &= ~XBBF_RESOURCE_SHORTAGE;
SLIST_INSERT_HEAD(&xbb->request_free_slist, req, links);
xbb->active_request_count--;
if ((xbb->flags & XBBF_SHUTDOWN) != 0) {
/*
* Shutdown is in progress. See if we can
* progress further now that one more request
* has completed and been returned to the
* free pool.
*/
xbb_shutdown(xbb);
}
mtx_unlock(&xbb->lock);
if (wake_thread != 0)
taskqueue_enqueue(xbb->io_taskqueue, &xbb->io_task);
}
/**
* Given a page index and 512b sector offset within that page,
* calculate an offset into a request's kva region.
*
* \param req The request structure whose kva region will be accessed.
* \param pagenr The page index used to compute the kva offset.
* \param sector The 512b sector index used to compute the page relative
* kva offset.
*
* \return The computed global KVA offset.
*/
static inline uint8_t *
xbb_req_vaddr(struct xbb_xen_req *req, int pagenr, int sector)
{
return (req->kva + (PAGE_SIZE * pagenr) + (sector << 9));
}
#ifdef XBB_USE_BOUNCE_BUFFERS
/**
* Given a page index and 512b sector offset within that page,
* calculate an offset into a request's local bounce memory region.
*
* \param req The request structure whose bounce region will be accessed.
* \param pagenr The page index used to compute the bounce offset.
* \param sector The 512b sector index used to compute the page relative
* bounce offset.
*
* \return The computed global bounce buffer address.
*/
static inline uint8_t *
xbb_req_bounce_addr(struct xbb_xen_req *req, int pagenr, int sector)
{
return (req->bounce + (PAGE_SIZE * pagenr) + (sector << 9));
}
#endif
/**
* Given a page number and 512b sector offset within that page,
* calculate an offset into the request's memory region that the
* underlying backend device/file should use for I/O.
*
* \param req The request structure whose I/O region will be accessed.
* \param pagenr The page index used to compute the I/O offset.
* \param sector The 512b sector index used to compute the page relative
* I/O offset.
*
* \return The computed global I/O address.
*
* Depending on configuration, this will either be a local bounce buffer
* or a pointer to the memory mapped in from the front-end domain for
* this request.
*/
static inline uint8_t *
xbb_req_ioaddr(struct xbb_xen_req *req, int pagenr, int sector)
{
#ifdef XBB_USE_BOUNCE_BUFFERS
return (xbb_req_bounce_addr(req, pagenr, sector));
#else
return (xbb_req_vaddr(req, pagenr, sector));
#endif
}
/**
* Given a page index and 512b sector offset within that page, calculate
* an offset into the local psuedo-physical address space used to map a
* front-end's request data into a request.
*
* \param req The request structure whose pseudo-physical region
* will be accessed.
* \param pagenr The page index used to compute the pseudo-physical offset.
* \param sector The 512b sector index used to compute the page relative
* pseudo-physical offset.
*
* \return The computed global pseudo-phsyical address.
*
* Depending on configuration, this will either be a local bounce buffer
* or a pointer to the memory mapped in from the front-end domain for
* this request.
*/
static inline uintptr_t
xbb_req_gntaddr(struct xbb_xen_req *req, int pagenr, int sector)
{
return ((uintptr_t)(req->gnt_base
+ (PAGE_SIZE * pagenr) + (sector << 9)));
}
/**
* Unmap the front-end pages associated with this I/O request.
*
* \param req The request structure to unmap.
*/
static void
xbb_unmap_req(struct xbb_xen_req *req)
{
struct gnttab_unmap_grant_ref unmap[XBB_MAX_SEGMENTS_PER_REQUEST];
u_int i;
u_int invcount;
int error;
invcount = 0;
for (i = 0; i < req->nr_pages; i++) {
if (req->gnt_handles[i] == GRANT_REF_INVALID)
continue;
unmap[invcount].host_addr = xbb_req_gntaddr(req, i, 0);
unmap[invcount].dev_bus_addr = 0;
unmap[invcount].handle = req->gnt_handles[i];
req->gnt_handles[i] = GRANT_REF_INVALID;
invcount++;
}
error = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
unmap, invcount);
KASSERT(error == 0, ("Grant table operation failed"));
}
/**
* Create and transmit a response to a blkif request.
*
* \param xbb Per-instance xbb configuration structure.
* \param req The request structure to which to respond.
* \param status The status code to report. See BLKIF_RSP_*
* in sys/xen/interface/io/blkif.h.
*/
static void
xbb_send_response(struct xbb_softc *xbb, struct xbb_xen_req *req, int status)
{
blkif_response_t *resp;
int more_to_do;
int notify;
more_to_do = 0;
/*
* Place on the response ring for the relevant domain.
* For now, only the spacing between entries is different
* in the different ABIs, not the response entry layout.
*/
mtx_lock(&xbb->lock);
switch (xbb->abi) {
case BLKIF_PROTOCOL_NATIVE:
resp = RING_GET_RESPONSE(&xbb->rings.native,
xbb->rings.native.rsp_prod_pvt);
break;
case BLKIF_PROTOCOL_X86_32:
resp = (blkif_response_t *)
RING_GET_RESPONSE(&xbb->rings.x86_32,
xbb->rings.x86_32.rsp_prod_pvt);
break;
case BLKIF_PROTOCOL_X86_64:
resp = (blkif_response_t *)
RING_GET_RESPONSE(&xbb->rings.x86_64,
xbb->rings.x86_64.rsp_prod_pvt);
break;
default:
panic("Unexpected blkif protocol ABI.");
}
resp->id = req->id;
resp->operation = req->operation;
resp->status = status;
xbb->rings.common.rsp_prod_pvt += BLKIF_SEGS_TO_BLOCKS(req->nr_pages);
RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&xbb->rings.common, notify);
if (xbb->rings.common.rsp_prod_pvt == xbb->rings.common.req_cons) {
/*
* Tail check for pending requests. Allows frontend to avoid
* notifications if requests are already in flight (lower
* overheads and promotes batching).
*/
RING_FINAL_CHECK_FOR_REQUESTS(&xbb->rings.common, more_to_do);
} else if (RING_HAS_UNCONSUMED_REQUESTS(&xbb->rings.common)) {
more_to_do = 1;
}
mtx_unlock(&xbb->lock);
if (more_to_do)
taskqueue_enqueue(xbb->io_taskqueue, &xbb->io_task);
if (notify)
notify_remote_via_irq(xbb->irq);
}
/**
* Completion handler for buffer I/O requests issued by the device
* backend driver.
*
* \param bio The buffer I/O request on which to perform completion
* processing.
*/
static void
xbb_bio_done(struct bio *bio)
{
struct xbb_softc *xbb;
struct xbb_xen_req *req;
req = bio->bio_caller1;
xbb = req->xbb;
/* Only include transferred I/O in stats. */
req->nr_512b_sectors -= bio->bio_resid >> 9;
if (bio->bio_error) {
DPRINTF("BIO returned error %d for operation on device %s\n",
bio->bio_error, xbb->dev_name);
req->status = BLKIF_RSP_ERROR;
if (bio->bio_error == ENXIO
&& xenbus_get_state(xbb->dev) == XenbusStateConnected) {
/*
* Backend device has disappeared. Signal the
* front-end that we (the device proxy) want to
* go away.
*/
xenbus_set_state(xbb->dev, XenbusStateClosing);
}
}
#ifdef XBB_USE_BOUNCE_BUFFERS
if (bio->bio_cmd == BIO_READ) {
vm_offset_t kva_offset;
kva_offset = (vm_offset_t)bio->bio_data
- (vm_offset_t)req->bounce;
memcpy((uint8_t *)req->kva + kva_offset,
bio->bio_data, bio->bio_bcount);
}
#endif /* XBB_USE_BOUNCE_BUFFERS */
if (atomic_fetchadd_int(&req->pendcnt, -1) == 1) {
xbb_unmap_req(req);
xbb_send_response(xbb, req, req->status);
devstat_end_transaction(xbb->xbb_stats,
/*bytes*/req->nr_512b_sectors << 9,
req->ds_tag_type,
req->ds_trans_type,
/*now*/NULL,
/*then*/&req->ds_t0);
xbb_release_req(xbb, req);
}
g_destroy_bio(bio);
}
/**
* Parse a blkif request into an internal request structure and send
* it to the backend for processing.
*
* \param xbb Per-instance xbb configuration structure.
* \param ring_req Front-end's I/O request as pulled from the shared
* communication ring.
* \param req Allocated internal request structure.
* \param req_ring_idx The location of ring_req within the shared
* communication ring.
*
* This routine performs the backend common aspects of request parsing
* including compiling an internal request structure, parsing the S/G
* list and any secondary ring requests in which they may reside, and
* the mapping of front-end I/O pages into our domain.
*/
static void
xbb_dispatch_io(struct xbb_softc *xbb, blkif_request_t *ring_req,
struct xbb_xen_req *req, RING_IDX req_ring_idx)
{
struct gnttab_map_grant_ref maps[XBB_MAX_SEGMENTS_PER_REQUEST];
struct xbb_sg *xbb_sg;
struct gnttab_map_grant_ref *map;
struct blkif_request_segment *sg;
struct blkif_request_segment *last_block_sg;
u_int nseg;
u_int seg_idx;
u_int block_segs;
int nr_sects;
int operation;
uint8_t bio_flags;
int error;
nseg = ring_req->nr_segments;
nr_sects = 0;
req->xbb = xbb;
req->id = ring_req->id;
req->operation = ring_req->operation;
req->status = BLKIF_RSP_OKAY;
req->ds_tag_type = DEVSTAT_TAG_SIMPLE;
req->nr_pages = nseg;
req->nr_512b_sectors = 0;
bio_flags = 0;
sg = NULL;
binuptime(&req->ds_t0);
devstat_start_transaction(xbb->xbb_stats, &req->ds_t0);
switch (req->operation) {
case BLKIF_OP_WRITE_BARRIER:
bio_flags |= BIO_ORDERED;
req->ds_tag_type = DEVSTAT_TAG_ORDERED;
/* FALLTHROUGH */
case BLKIF_OP_WRITE:
operation = BIO_WRITE;
req->ds_trans_type = DEVSTAT_WRITE;
if ((xbb->flags & XBBF_READ_ONLY) != 0) {
DPRINTF("Attempt to write to read only device %s\n",
xbb->dev_name);
goto fail_send_response;
}
break;
case BLKIF_OP_READ:
operation = BIO_READ;
req->ds_trans_type = DEVSTAT_READ;
break;
case BLKIF_OP_FLUSH_DISKCACHE:
operation = BIO_FLUSH;
req->ds_tag_type = DEVSTAT_TAG_ORDERED;
req->ds_trans_type = DEVSTAT_NO_DATA;
goto do_dispatch;
/*NOTREACHED*/
default:
DPRINTF("error: unknown block io operation [%d]\n",
req->operation);
goto fail_send_response;
}
/* Check that number of segments is sane. */
if (unlikely(nseg == 0)
|| unlikely(nseg > xbb->max_request_segments)) {
DPRINTF("Bad number of segments in request (%d)\n", nseg);
goto fail_send_response;
}
map = maps;
xbb_sg = xbb->xbb_sgs;
block_segs = MIN(req->nr_pages, BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK);
sg = ring_req->seg;
last_block_sg = sg + block_segs;
seg_idx = 0;
while (1) {
while (sg < last_block_sg) {
xbb_sg->first_sect = sg->first_sect;
xbb_sg->last_sect = sg->last_sect;
xbb_sg->nsect =
(int8_t)(sg->last_sect - sg->first_sect + 1);
if ((sg->last_sect >= (PAGE_SIZE >> 9))
|| (xbb_sg->nsect <= 0))
goto fail_send_response;
nr_sects += xbb_sg->nsect;
map->host_addr = xbb_req_gntaddr(req, seg_idx,
/*sector*/0);
map->flags = GNTMAP_host_map;
map->ref = sg->gref;
map->dom = xbb->otherend_id;
if (operation == BIO_WRITE)
map->flags |= GNTMAP_readonly;
sg++;
map++;
xbb_sg++;
seg_idx++;
}
block_segs = MIN(nseg - seg_idx,
BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK);
if (block_segs == 0)
break;
/*
* Fetch the next request block full of SG elements.
* For now, only the spacing between entries is different
* in the different ABIs, not the sg entry layout.
*/
req_ring_idx++;
switch (xbb->abi) {
case BLKIF_PROTOCOL_NATIVE:
sg = BLKRING_GET_SG_REQUEST(&xbb->rings.native,
req_ring_idx);
break;
case BLKIF_PROTOCOL_X86_32:
{
sg = BLKRING_GET_SG_REQUEST(&xbb->rings.x86_32,
req_ring_idx);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
sg = BLKRING_GET_SG_REQUEST(&xbb->rings.x86_64,
req_ring_idx);
break;
}
default:
panic("Unexpected blkif protocol ABI.");
/* NOTREACHED */
}
last_block_sg = sg + block_segs;
}
/* Convert to the disk's sector size */
req->nr_512b_sectors = nr_sects;
nr_sects = (nr_sects << 9) >> xbb->sector_size_shift;
if ((req->nr_512b_sectors & ((xbb->sector_size >> 9) - 1)) != 0) {
device_printf(xbb->dev, "%s: I/O size (%d) is not a multiple "
"of the backing store sector size (%d)\n",
__func__, req->nr_512b_sectors << 9,
xbb->sector_size);
goto fail_send_response;
}
error = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
maps, req->nr_pages);
if (error != 0)
panic("Grant table operation failed (%d)", error);
for (seg_idx = 0, map = maps; seg_idx < nseg; seg_idx++, map++) {
if (unlikely(map->status != 0)) {
DPRINTF("invalid buffer -- could not remap it (%d)\n",
map->status);
DPRINTF("Mapping(%d): Host Addr 0x%lx, flags 0x%x "
"ref 0x%x, dom %d\n", seg_idx,
map->host_addr, map->flags, map->ref,
map->dom);
goto fail_unmap_req;
}
req->gnt_handles[seg_idx] = map->handle;
}
if (ring_req->sector_number + nr_sects > xbb->media_num_sectors) {
DPRINTF("%s of [%" PRIu64 ",%" PRIu64 "] "
"extends past end of device %s\n",
operation == BIO_READ ? "read" : "write",
ring_req->sector_number,
ring_req->sector_number + nr_sects, xbb->dev_name);
goto fail_unmap_req;
}
do_dispatch:
error = xbb->dispatch_io(xbb,
ring_req,
req,
nseg,
operation,
bio_flags);
if (error != 0) {
if (operation == BIO_FLUSH)
goto fail_send_response;
else
goto fail_unmap_req;
}
return;
fail_unmap_req:
xbb_unmap_req(req);
/* FALLTHROUGH */
fail_send_response:
xbb_send_response(xbb, req, BLKIF_RSP_ERROR);
xbb_release_req(xbb, req);
devstat_end_transaction(xbb->xbb_stats,
/*bytes*/0,
req->ds_tag_type,
req->ds_trans_type,
/*now*/NULL,
/*then*/&req->ds_t0);
}
/**
* Process incoming requests from the shared communication ring in response
* to a signal on the ring's event channel.
*
* \param context Callback argument registerd during task initialization -
* the xbb_softc for this instance.
* \param pending The number of taskqueue_enqueue events that have
* occurred since this handler was last run.
*/
static void
xbb_run_queue(void *context, int pending)
{
struct xbb_softc *xbb;
blkif_back_rings_t *rings;
RING_IDX rp;
xbb = (struct xbb_softc *)context;
rings = &xbb->rings;
/*
* Cache req_prod to avoid accessing a cache line shared
* with the frontend.
*/
rp = rings->common.sring->req_prod;
/* Ensure we see queued requests up to 'rp'. */
rmb();
/**
* Run so long as there is work to consume and the generation
* of a response will not overflow the ring.
*
* @note There's a 1 to 1 relationship between requests and responses,
* so an overflow should never occur. This test is to protect
* our domain from digesting bogus data. Shouldn't we log this?
*/
while (rings->common.req_cons != rp
&& RING_REQUEST_CONS_OVERFLOW(&rings->common,
rings->common.req_cons) == 0) {
blkif_request_t ring_req_storage;
blkif_request_t *ring_req;
struct xbb_xen_req *req;
RING_IDX req_ring_idx;
req = xbb_get_req(xbb);
if (req == NULL) {
/*
* Resource shortage has been recorded.
* We'll be scheduled to run once a request
* object frees up due to a completion.
*/
break;
}
switch (xbb->abi) {
case BLKIF_PROTOCOL_NATIVE:
ring_req = RING_GET_REQUEST(&xbb->rings.native,
rings->common.req_cons);
break;
case BLKIF_PROTOCOL_X86_32:
{
struct blkif_x86_32_request *ring_req32;
ring_req32 = RING_GET_REQUEST(&xbb->rings.x86_32,
rings->common.req_cons);
blkif_get_x86_32_req(&ring_req_storage, ring_req32);
ring_req = &ring_req_storage;
break;
}
case BLKIF_PROTOCOL_X86_64:
{
struct blkif_x86_64_request *ring_req64;
ring_req64 = RING_GET_REQUEST(&xbb->rings.x86_64,
rings->common.req_cons);
blkif_get_x86_64_req(&ring_req_storage, ring_req64);
ring_req = &ring_req_storage;
break;
}
default:
panic("Unexpected blkif protocol ABI.");
/* NOTREACHED */
}
/*
* Signify that we can overwrite this request with a
* response by incrementing our consumer index. The
* response won't be generated until after we've already
* consumed all necessary data out of the version of the
* request in the ring buffer (for native mode). We
* must update the consumer index before issueing back-end
* I/O so there is no possibility that it will complete
* and a response be generated before we make room in
* the queue for that response.
*/
req_ring_idx = xbb->rings.common.req_cons;
xbb->rings.common.req_cons +=
BLKIF_SEGS_TO_BLOCKS(ring_req->nr_segments);
xbb_dispatch_io(xbb, ring_req, req, req_ring_idx);
}
}
/**
* Interrupt handler bound to the shared ring's event channel.
*
* \param arg Callback argument registerd during event channel
* binding - the xbb_softc for this instance.
*/
static void
xbb_intr(void *arg)
{
struct xbb_softc *xbb;
/* Defer to kernel thread. */
xbb = (struct xbb_softc *)arg;
taskqueue_enqueue(xbb->io_taskqueue, &xbb->io_task);
}
/*----------------------------- Backend Handlers -----------------------------*/
/**
* Backend handler for character device access.
*
* \param xbb Per-instance xbb configuration structure.
* \param ring_req Front-end's I/O request as pulled from the shared
* communication ring.
* \param req Allocated internal request structure.
* \param nseg The number of valid segments for this request in
* xbb->xbb_sgs.
* \param operation BIO_* I/O operation code.
* \param bio_flags Additional bio_flag data to pass to any generated
* bios (e.g. BIO_ORDERED)..
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_dispatch_dev(struct xbb_softc *xbb, blkif_request_t *ring_req,
struct xbb_xen_req *req, int nseg, int operation,
int bio_flags)
{
struct xbb_dev_data *dev_data;
struct bio *bios[XBB_MAX_SEGMENTS_PER_REQUEST];
off_t bio_offset;
struct bio *bio;
struct xbb_sg *xbb_sg;
u_int nbio;
u_int bio_idx;
u_int seg_idx;
int error;
dev_data = &xbb->backend.dev;
bio_offset = (off_t)ring_req->sector_number
<< xbb->sector_size_shift;
error = 0;
nbio = 0;
bio_idx = 0;
if (operation == BIO_FLUSH) {
bio = g_new_bio();
if (unlikely(bio == NULL)) {
DPRINTF("Unable to allocate bio for BIO_FLUSH\n");
error = ENOMEM;
return (error);
}
bio->bio_cmd = BIO_FLUSH;
bio->bio_flags |= BIO_ORDERED;
bio->bio_dev = dev_data->cdev;
bio->bio_offset = 0;
bio->bio_data = 0;
bio->bio_done = xbb_bio_done;
bio->bio_caller1 = req;
bio->bio_pblkno = 0;
req->pendcnt = 1;
(*dev_data->csw->d_strategy)(bios[bio_idx]);
return (0);
}
for (seg_idx = 0, bio = NULL, xbb_sg = xbb->xbb_sgs;
seg_idx < nseg;
seg_idx++, xbb_sg++) {
/*
* KVA will not be contiguous, so any additional
* I/O will need to be represented in a new bio.
*/
if ((bio != NULL)
&& (xbb_sg->first_sect != 0)) {
if ((bio->bio_length & (xbb->sector_size - 1)) != 0) {
printf("%s: Discontiguous I/O request from "
"domain %d ends on non-sector "
"boundary\n", __func__,
xbb->otherend_id);
error = EINVAL;
goto fail_free_bios;
}
bio = NULL;
}
if (bio == NULL) {
/*
* Make sure that the start of this bio is aligned
* to a device sector.
*/
if ((bio_offset & (xbb->sector_size - 1)) != 0) {
printf("%s: Misaligned I/O request from "
"domain %d\n", __func__,
xbb->otherend_id);
error = EINVAL;
goto fail_free_bios;
}
bio = bios[nbio++] = g_new_bio();
if (unlikely(bio == NULL)) {
error = ENOMEM;
goto fail_free_bios;
}
bio->bio_cmd = operation;
bio->bio_flags |= bio_flags;
bio->bio_dev = dev_data->cdev;
bio->bio_offset = bio_offset;
bio->bio_data = xbb_req_ioaddr(req, seg_idx,
xbb_sg->first_sect);
bio->bio_done = xbb_bio_done;
bio->bio_caller1 = req;
bio->bio_pblkno = bio_offset
>> xbb->sector_size_shift;
}
bio->bio_length += xbb_sg->nsect << 9;
bio->bio_bcount = bio->bio_length;
bio_offset += xbb_sg->nsect << 9;
if (xbb_sg->last_sect != (PAGE_SIZE - 512) >> 9) {
if ((bio->bio_length & (xbb->sector_size - 1)) != 0) {
printf("%s: Discontiguous I/O request from "
"domain %d ends on non-sector "
"boundary\n", __func__,
xbb->otherend_id);
error = EINVAL;
goto fail_free_bios;
}
/*
* KVA will not be contiguous, so any additional
* I/O will need to be represented in a new bio.
*/
bio = NULL;
}
}
req->pendcnt = nbio;
for (bio_idx = 0; bio_idx < nbio; bio_idx++)
{
#ifdef XBB_USE_BOUNCE_BUFFERS
vm_offset_t kva_offset;
kva_offset = (vm_offset_t)bios[bio_idx]->bio_data
- (vm_offset_t)req->bounce;
if (operation == BIO_WRITE) {
memcpy(bios[bio_idx]->bio_data,
(uint8_t *)req->kva + kva_offset,
bios[bio_idx]->bio_bcount);
}
#endif
(*dev_data->csw->d_strategy)(bios[bio_idx]);
}
return (error);
fail_free_bios:
for (bio_idx = 0; bio_idx < (nbio-1); bio_idx++)
g_destroy_bio(bios[bio_idx]);
return (error);
}
/**
* Backend handler for file access.
*
* \param xbb Per-instance xbb configuration structure.
* \param ring_req Front-end's I/O request as pulled from the shared
* communication ring.
* \param req Allocated internal request structure.
* \param nseg The number of valid segments for this request in
* xbb->xbb_sgs.
* \param operation BIO_* I/O operation code.
* \param bio_flags Additional bio_flag data to pass to any generated bios
* (e.g. BIO_ORDERED)..
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_dispatch_file(struct xbb_softc *xbb, blkif_request_t *ring_req,
struct xbb_xen_req *req, int nseg, int operation,
int flags)
{
struct xbb_file_data *file_data;
u_int seg_idx;
struct uio xuio;
struct xbb_sg *xbb_sg;
struct iovec *xiovec;
#ifdef XBB_USE_BOUNCE_BUFFERS
void **p_vaddr;
int saved_uio_iovcnt;
#endif /* XBB_USE_BOUNCE_BUFFERS */
int vfs_is_locked;
int error;
file_data = &xbb->backend.file;
error = 0;
bzero(&xuio, sizeof(xuio));
req->pendcnt = 0;
switch (operation) {
case BIO_READ:
xuio.uio_rw = UIO_READ;
break;
case BIO_WRITE:
xuio.uio_rw = UIO_WRITE;
break;
case BIO_FLUSH: {
struct mount *mountpoint;
vfs_is_locked = VFS_LOCK_GIANT(xbb->vn->v_mount);
(void) vn_start_write(xbb->vn, &mountpoint, V_WAIT);
vn_lock(xbb->vn, LK_EXCLUSIVE | LK_RETRY);
error = VOP_FSYNC(xbb->vn, MNT_WAIT, curthread);
VOP_UNLOCK(xbb->vn, 0);
vn_finished_write(mountpoint);
VFS_UNLOCK_GIANT(vfs_is_locked);
goto bailout_send_response;
/* NOTREACHED */
}
default:
panic("invalid operation %d", operation);
/* NOTREACHED */
}
xuio.uio_offset = (vm_offset_t)ring_req->sector_number
<< xbb->sector_size_shift;
xuio.uio_segflg = UIO_SYSSPACE;
xuio.uio_iov = file_data->xiovecs;
xuio.uio_iovcnt = 0;
for (seg_idx = 0, xiovec = NULL, xbb_sg = xbb->xbb_sgs;
seg_idx < nseg; seg_idx++, xbb_sg++) {
/*
* If the first sector is not 0, the KVA will not be
* contiguous and we'll need to go on to another segment.
*/
if (xbb_sg->first_sect != 0)
xiovec = NULL;
if (xiovec == NULL) {
xiovec = &file_data->xiovecs[xuio.uio_iovcnt];
xiovec->iov_base = xbb_req_ioaddr(req, seg_idx,
xbb_sg->first_sect);
#ifdef XBB_USE_BOUNCE_BUFFERS
/*
* Store the address of the incoming buffer at this
* particular offset as well, so we can do the copy
* later without having to do more work to
* recalculate this address.
*/
p_vaddr = &file_data->xiovecs_vaddr[xuio.uio_iovcnt];
*p_vaddr = xbb_req_vaddr(req, seg_idx,
xbb_sg->first_sect);
#endif /* XBB_USE_BOUNCE_BUFFERS */
xiovec->iov_len = 0;
xuio.uio_iovcnt++;
}
xiovec->iov_len += xbb_sg->nsect << 9;
xuio.uio_resid += xbb_sg->nsect << 9;
/*
* If the last sector is not the full page size count,
* the next segment will not be contiguous in KVA and we
* need a new iovec.
*/
if (xbb_sg->last_sect != (PAGE_SIZE - 512) >> 9)
xiovec = NULL;
}
xuio.uio_td = curthread;
#ifdef XBB_USE_BOUNCE_BUFFERS
saved_uio_iovcnt = xuio.uio_iovcnt;
if (operation == BIO_WRITE) {
/* Copy the write data to the local buffer. */
for (seg_idx = 0, p_vaddr = file_data->xiovecs_vaddr,
xiovec = xuio.uio_iov; seg_idx < xuio.uio_iovcnt;
seg_idx++, xiovec++, p_vaddr++) {
memcpy(xiovec->iov_base, *p_vaddr, xiovec->iov_len);
}
} else {
/*
* We only need to save off the iovecs in the case of a
* read, because the copy for the read happens after the
* VOP_READ(). (The uio will get modified in that call
* sequence.)
*/
memcpy(file_data->saved_xiovecs, xuio.uio_iov,
xuio.uio_iovcnt * sizeof(xuio.uio_iov[0]));
}
#endif /* XBB_USE_BOUNCE_BUFFERS */
vfs_is_locked = VFS_LOCK_GIANT(xbb->vn->v_mount);
switch (operation) {
case BIO_READ:
vn_lock(xbb->vn, LK_EXCLUSIVE | LK_RETRY);
/*
* UFS pays attention to IO_DIRECT for reads. If the
* DIRECTIO option is configured into the kernel, it calls
* ffs_rawread(). But that only works for single-segment
* uios with user space addresses. In our case, with a
* kernel uio, it still reads into the buffer cache, but it
* will just try to release the buffer from the cache later
* on in ffs_read().
*
* ZFS does not pay attention to IO_DIRECT for reads.
*
* UFS does not pay attention to IO_SYNC for reads.
*
* ZFS pays attention to IO_SYNC (which translates into the
* Solaris define FRSYNC for zfs_read()) for reads. It
* attempts to sync the file before reading.
*
* So, to attempt to provide some barrier semantics in the
* BIO_ORDERED case, set both IO_DIRECT and IO_SYNC.
*/
error = VOP_READ(xbb->vn, &xuio, (flags & BIO_ORDERED) ?
(IO_DIRECT|IO_SYNC) : 0, file_data->cred);
VOP_UNLOCK(xbb->vn, 0);
break;
case BIO_WRITE: {
struct mount *mountpoint;
(void)vn_start_write(xbb->vn, &mountpoint, V_WAIT);
vn_lock(xbb->vn, LK_EXCLUSIVE | LK_RETRY);
/*
* UFS pays attention to IO_DIRECT for writes. The write
* is done asynchronously. (Normally the write would just
* get put into cache.
*
* UFS pays attention to IO_SYNC for writes. It will
* attempt to write the buffer out synchronously if that
* flag is set.
*
* ZFS does not pay attention to IO_DIRECT for writes.
*
* ZFS pays attention to IO_SYNC (a.k.a. FSYNC or FRSYNC)
* for writes. It will flush the transaction from the
* cache before returning.
*
* So if we've got the BIO_ORDERED flag set, we want
* IO_SYNC in either the UFS or ZFS case.
*/
error = VOP_WRITE(xbb->vn, &xuio, (flags & BIO_ORDERED) ?
IO_SYNC : 0, file_data->cred);
VOP_UNLOCK(xbb->vn, 0);
vn_finished_write(mountpoint);
break;
}
default:
panic("invalid operation %d", operation);
/* NOTREACHED */
}
VFS_UNLOCK_GIANT(vfs_is_locked);
#ifdef XBB_USE_BOUNCE_BUFFERS
/* We only need to copy here for read operations */
if (operation == BIO_READ) {
for (seg_idx = 0, p_vaddr = file_data->xiovecs_vaddr,
xiovec = file_data->saved_xiovecs;
seg_idx < saved_uio_iovcnt; seg_idx++,
xiovec++, p_vaddr++) {
/*
* Note that we have to use the copy of the
* io vector we made above. uiomove() modifies
* the uio and its referenced vector as uiomove
* performs the copy, so we can't rely on any
* state from the original uio.
*/
memcpy(*p_vaddr, xiovec->iov_base, xiovec->iov_len);
}
}
#endif /* XBB_USE_BOUNCE_BUFFERS */
bailout_send_response:
/*
* All I/O is already done, send the response. A lock is not
* necessary here because we're single threaded, and therefore the
* only context accessing this request right now. If that changes,
* we may need some locking here.
*/
xbb_unmap_req(req);
xbb_send_response(xbb, req, (error == 0) ? BLKIF_RSP_OKAY :
BLKIF_RSP_ERROR);
devstat_end_transaction(xbb->xbb_stats,
/*bytes*/error == 0 ? req->nr_512b_sectors << 9
: 0,
req->ds_tag_type,
req->ds_trans_type,
/*now*/NULL,
/*then*/&req->ds_t0);
xbb_release_req(xbb, req);
return (0);
}
/*--------------------------- Backend Configuration --------------------------*/
/**
* Close and cleanup any backend device/file specific state for this
* block back instance.
*
* \param xbb Per-instance xbb configuration structure.
*/
static void
xbb_close_backend(struct xbb_softc *xbb)
{
DROP_GIANT();
DPRINTF("closing dev=%s\n", xbb->dev_name);
if (xbb->vn) {
int flags = FREAD;
int vfs_is_locked = 0;
if ((xbb->flags & XBBF_READ_ONLY) == 0)
flags |= FWRITE;
switch (xbb->device_type) {
case XBB_TYPE_DISK:
if (xbb->backend.dev.csw) {
dev_relthread(xbb->backend.dev.cdev,
xbb->backend.dev.dev_ref);
xbb->backend.dev.csw = NULL;
xbb->backend.dev.cdev = NULL;
}
break;
case XBB_TYPE_FILE:
vfs_is_locked = VFS_LOCK_GIANT(xbb->vn->v_mount);
break;
case XBB_TYPE_NONE:
default:
panic("Unexpected backend type.");
break;
}
(void)vn_close(xbb->vn, flags, NOCRED, curthread);
xbb->vn = NULL;
switch (xbb->device_type) {
case XBB_TYPE_DISK:
break;
case XBB_TYPE_FILE:
VFS_UNLOCK_GIANT(vfs_is_locked);
if (xbb->backend.file.cred != NULL) {
crfree(xbb->backend.file.cred);
xbb->backend.file.cred = NULL;
}
break;
case XBB_TYPE_NONE:
default:
panic("Unexpected backend type.");
break;
}
}
PICKUP_GIANT();
}
/**
* Open a character device to be used for backend I/O.
*
* \param xbb Per-instance xbb configuration structure.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_open_dev(struct xbb_softc *xbb)
{
struct vattr vattr;
struct cdev *dev;
struct cdevsw *devsw;
int error;
xbb->device_type = XBB_TYPE_DISK;
xbb->dispatch_io = xbb_dispatch_dev;
xbb->backend.dev.cdev = xbb->vn->v_rdev;
xbb->backend.dev.csw = dev_refthread(xbb->backend.dev.cdev,
&xbb->backend.dev.dev_ref);
if (xbb->backend.dev.csw == NULL)
panic("Unable to retrieve device switch");
error = VOP_GETATTR(xbb->vn, &vattr, NOCRED);
if (error) {
xenbus_dev_fatal(xbb->dev, error, "error getting "
"vnode attributes for device %s",
xbb->dev_name);
return (error);
}
dev = xbb->vn->v_rdev;
devsw = dev->si_devsw;
if (!devsw->d_ioctl) {
xenbus_dev_fatal(xbb->dev, ENODEV, "no d_ioctl for "
"device %s!", xbb->dev_name);
return (ENODEV);
}
error = devsw->d_ioctl(dev, DIOCGSECTORSIZE,
(caddr_t)&xbb->sector_size, FREAD,
curthread);
if (error) {
xenbus_dev_fatal(xbb->dev, error,
"error calling ioctl DIOCGSECTORSIZE "
"for device %s", xbb->dev_name);
return (error);
}
error = devsw->d_ioctl(dev, DIOCGMEDIASIZE,
(caddr_t)&xbb->media_size, FREAD,
curthread);
if (error) {
xenbus_dev_fatal(xbb->dev, error,
"error calling ioctl DIOCGMEDIASIZE "
"for device %s", xbb->dev_name);
return (error);
}
return (0);
}
/**
* Open a file to be used for backend I/O.
*
* \param xbb Per-instance xbb configuration structure.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_open_file(struct xbb_softc *xbb)
{
struct xbb_file_data *file_data;
struct vattr vattr;
int error;
file_data = &xbb->backend.file;
xbb->device_type = XBB_TYPE_FILE;
xbb->dispatch_io = xbb_dispatch_file;
error = VOP_GETATTR(xbb->vn, &vattr, curthread->td_ucred);
if (error != 0) {
xenbus_dev_fatal(xbb->dev, error,
"error calling VOP_GETATTR()"
"for file %s", xbb->dev_name);
return (error);
}
/*
* Verify that we have the ability to upgrade to exclusive
* access on this file so we can trap errors at open instead
* of reporting them during first access.
*/
if (VOP_ISLOCKED(xbb->vn) != LK_EXCLUSIVE) {
vn_lock(xbb->vn, LK_UPGRADE | LK_RETRY);
if (xbb->vn->v_iflag & VI_DOOMED) {
error = EBADF;
xenbus_dev_fatal(xbb->dev, error,
"error locking file %s",
xbb->dev_name);
return (error);
}
}
file_data->cred = crhold(curthread->td_ucred);
xbb->media_size = vattr.va_size;
/*
* XXX KDM vattr.va_blocksize may be larger than 512 bytes here.
* With ZFS, it is 131072 bytes. Block sizes that large don't work
* with disklabel and UFS on FreeBSD at least. Large block sizes
* may not work with other OSes as well. So just export a sector
* size of 512 bytes, which should work with any OS or
* application. Since our backing is a file, any block size will
* work fine for the backing store.
*/
#if 0
xbb->sector_size = vattr.va_blocksize;
#endif
xbb->sector_size = 512;
/*
* Sanity check. The media size has to be at least one
* sector long.
*/
if (xbb->media_size < xbb->sector_size) {
error = EINVAL;
xenbus_dev_fatal(xbb->dev, error,
"file %s size %ju < block size %u",
xbb->dev_name,
(uintmax_t)xbb->media_size,
xbb->sector_size);
}
return (error);
}
/**
* Open the backend provider for this connection.
*
* \param xbb Per-instance xbb configuration structure.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_open_backend(struct xbb_softc *xbb)
{
struct nameidata nd;
int flags;
int error;
int vfs_is_locked;
flags = FREAD;
error = 0;
DPRINTF("opening dev=%s\n", xbb->dev_name);
if ((xbb->flags & XBBF_READ_ONLY) == 0)
flags |= FWRITE;
if (!curthread->td_proc->p_fd->fd_cdir) {
curthread->td_proc->p_fd->fd_cdir = rootvnode;
VREF(rootvnode);
}
if (!curthread->td_proc->p_fd->fd_rdir) {
curthread->td_proc->p_fd->fd_rdir = rootvnode;
VREF(rootvnode);
}
if (!curthread->td_proc->p_fd->fd_jdir) {
curthread->td_proc->p_fd->fd_jdir = rootvnode;
VREF(rootvnode);
}
again:
NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, xbb->dev_name, curthread);
error = vn_open(&nd, &flags, 0, NULL);
if (error) {
/*
* This is the only reasonable guess we can make as far as
* path if the user doesn't give us a fully qualified path.
* If they want to specify a file, they need to specify the
* full path.
*/
if (xbb->dev_name[0] != '/') {
char *dev_path = "/dev/";
char *dev_name;
/* Try adding device path at beginning of name */
dev_name = malloc(strlen(xbb->dev_name)
+ strlen(dev_path) + 1,
M_XENBLOCKBACK, M_NOWAIT);
if (dev_name) {
sprintf(dev_name, "%s%s", dev_path,
xbb->dev_name);
free(xbb->dev_name, M_XENBLOCKBACK);
xbb->dev_name = dev_name;
goto again;
}
}
xenbus_dev_fatal(xbb->dev, error, "error opening device %s",
xbb->dev_name);
return (error);
}
vfs_is_locked = NDHASGIANT(&nd);
NDFREE(&nd, NDF_ONLY_PNBUF);
xbb->vn = nd.ni_vp;
/* We only support disks and files. */
if (vn_isdisk(xbb->vn, &error)) {
error = xbb_open_dev(xbb);
} else if (xbb->vn->v_type == VREG) {
error = xbb_open_file(xbb);
} else {
error = EINVAL;
xenbus_dev_fatal(xbb->dev, error, "%s is not a disk "
"or file", xbb->dev_name);
}
VOP_UNLOCK(xbb->vn, 0);
VFS_UNLOCK_GIANT(vfs_is_locked);
if (error != 0) {
xbb_close_backend(xbb);
return (error);
}
xbb->sector_size_shift = fls(xbb->sector_size) - 1;
xbb->media_num_sectors = xbb->media_size >> xbb->sector_size_shift;
DPRINTF("opened %s=%s sector_size=%u media_size=%" PRId64 "\n",
(xbb->device_type == XBB_TYPE_DISK) ? "dev" : "file",
xbb->dev_name, xbb->sector_size, xbb->media_size);
return (0);
}
/*------------------------ Inter-Domain Communication ------------------------*/
/**
* Cleanup all inter-domain communication mechanisms.
*
* \param xbb Per-instance xbb configuration structure.
*/
static void
xbb_disconnect(struct xbb_softc *xbb)
{
struct gnttab_unmap_grant_ref ops[XBB_MAX_RING_PAGES];
struct gnttab_unmap_grant_ref *op;
u_int ring_idx;
int error;
DPRINTF("\n");
if ((xbb->flags & XBBF_RING_CONNECTED) == 0)
return;
if (xbb->irq != 0) {
unbind_from_irqhandler(xbb->irq);
xbb->irq = 0;
}
for (ring_idx = 0, op = ops;
ring_idx < xbb->ring_config.ring_pages;
ring_idx++, op++) {
op->host_addr = xbb->ring_config.gnt_addr
+ (ring_idx * PAGE_SIZE);
op->dev_bus_addr = xbb->ring_config.bus_addr[ring_idx];
op->handle = xbb->ring_config.handle[ring_idx];
}
error = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, ops,
xbb->ring_config.ring_pages);
if (error != 0)
panic("Grant table op failed (%d)", error);
xbb->flags &= ~XBBF_RING_CONNECTED;
}
/**
* Map shared memory ring into domain local address space, initialize
* ring control structures, and bind an interrupt to the event channel
* used to notify us of ring changes.
*
* \param xbb Per-instance xbb configuration structure.
*/
static int
xbb_connect_ring(struct xbb_softc *xbb)
{
struct gnttab_map_grant_ref gnts[XBB_MAX_RING_PAGES];
struct gnttab_map_grant_ref *gnt;
u_int ring_idx;
int error;
if ((xbb->flags & XBBF_RING_CONNECTED) != 0)
return (0);
/*
* Kva for our ring is at the tail of the region of kva allocated
* by xbb_alloc_communication_mem().
*/
xbb->ring_config.va = xbb->kva
+ (xbb->kva_size
- (xbb->ring_config.ring_pages * PAGE_SIZE));
xbb->ring_config.gnt_addr = xbb->gnt_base_addr
+ (xbb->kva_size
- (xbb->ring_config.ring_pages * PAGE_SIZE));
for (ring_idx = 0, gnt = gnts;
ring_idx < xbb->ring_config.ring_pages;
ring_idx++, gnt++) {
gnt->host_addr = xbb->ring_config.gnt_addr
+ (ring_idx * PAGE_SIZE);
gnt->flags = GNTMAP_host_map;
gnt->ref = xbb->ring_config.ring_ref[ring_idx];
gnt->dom = xbb->otherend_id;
}
error = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, gnts,
xbb->ring_config.ring_pages);
if (error)
panic("blkback: Ring page grant table op failed (%d)", error);
for (ring_idx = 0, gnt = gnts;
ring_idx < xbb->ring_config.ring_pages;
ring_idx++, gnt++) {
if (gnt->status != 0) {
xbb->ring_config.va = 0;
xenbus_dev_fatal(xbb->dev, EACCES,
"Ring shared page mapping failed. "
"Status %d.", gnt->status);
return (EACCES);
}
xbb->ring_config.handle[ring_idx] = gnt->handle;
xbb->ring_config.bus_addr[ring_idx] = gnt->dev_bus_addr;
}
/* Initialize the ring based on ABI. */
switch (xbb->abi) {
case BLKIF_PROTOCOL_NATIVE:
{
blkif_sring_t *sring;
sring = (blkif_sring_t *)xbb->ring_config.va;
BACK_RING_INIT(&xbb->rings.native, sring,
xbb->ring_config.ring_pages * PAGE_SIZE);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
blkif_x86_32_sring_t *sring_x86_32;
sring_x86_32 = (blkif_x86_32_sring_t *)xbb->ring_config.va;
BACK_RING_INIT(&xbb->rings.x86_32, sring_x86_32,
xbb->ring_config.ring_pages * PAGE_SIZE);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
blkif_x86_64_sring_t *sring_x86_64;
sring_x86_64 = (blkif_x86_64_sring_t *)xbb->ring_config.va;
BACK_RING_INIT(&xbb->rings.x86_64, sring_x86_64,
xbb->ring_config.ring_pages * PAGE_SIZE);
break;
}
default:
panic("Unexpected blkif protocol ABI.");
}
xbb->flags |= XBBF_RING_CONNECTED;
error =
bind_interdomain_evtchn_to_irqhandler(xbb->otherend_id,
xbb->ring_config.evtchn,
device_get_nameunit(xbb->dev),
xbb_intr, /*arg*/xbb,
INTR_TYPE_BIO | INTR_MPSAFE,
&xbb->irq);
if (error) {
xbb_disconnect(xbb);
xenbus_dev_fatal(xbb->dev, error, "binding event channel");
return (error);
}
DPRINTF("rings connected!\n");
return 0;
}
/**
* Size KVA and pseudo-physical address allocations based on negotiated
* values for the size and number of I/O requests, and the size of our
* communication ring.
*
* \param xbb Per-instance xbb configuration structure.
*
* These address spaces are used to dynamically map pages in the
* front-end's domain into our own.
*/
static int
xbb_alloc_communication_mem(struct xbb_softc *xbb)
{
xbb->kva_size = (xbb->ring_config.ring_pages
+ (xbb->max_requests * xbb->max_request_segments))
* PAGE_SIZE;
#ifndef XENHVM
xbb->kva = kmem_alloc_nofault(kernel_map, xbb->kva_size);
if (xbb->kva == 0)
return (ENOMEM);
xbb->gnt_base_addr = xbb->kva;
#else /* XENHVM */
/*
* Reserve a range of pseudo physical memory that we can map
* into kva. These pages will only be backed by machine
* pages ("real memory") during the lifetime of front-end requests
* via grant table operations.
*/
xbb->pseudo_phys_res_id = 0;
xbb->pseudo_phys_res = bus_alloc_resource(xbb->dev, SYS_RES_MEMORY,
&xbb->pseudo_phys_res_id,
0, ~0, xbb->kva_size,
RF_ACTIVE);
if (xbb->pseudo_phys_res == NULL) {
xbb->kva = 0;
return (ENOMEM);
}
xbb->kva = (vm_offset_t)rman_get_virtual(xbb->pseudo_phys_res);
xbb->gnt_base_addr = rman_get_start(xbb->pseudo_phys_res);
#endif /* XENHVM */
return (0);
}
/**
* Free dynamically allocated KVA or pseudo-physical address allocations.
*
* \param xbb Per-instance xbb configuration structure.
*/
static void
xbb_free_communication_mem(struct xbb_softc *xbb)
{
if (xbb->kva != 0) {
#ifndef XENHVM
kmem_free(kernel_map, xbb->kva, xbb->kva_size);
#else
if (xbb->pseudo_phys_res != NULL) {
bus_release_resource(xbb->dev, SYS_RES_MEMORY,
xbb->pseudo_phys_res_id,
xbb->pseudo_phys_res);
xbb->pseudo_phys_res = NULL;
}
#endif
}
xbb->kva = 0;
xbb->gnt_base_addr = 0;
}
/**
* Collect front-end information from the XenStore.
*
* \param xbb Per-instance xbb configuration structure.
*/
static int
xbb_collect_frontend_info(struct xbb_softc *xbb)
{
char protocol_abi[64];
const char *otherend_path;
int error;
u_int ring_idx;
otherend_path = xenbus_get_otherend_path(xbb->dev);
/*
* Mandatory data (used in all versions of the protocol) first.
*/
error = xs_gather(XST_NIL, otherend_path,
"ring-ref", "%" PRIu32,
&xbb->ring_config.ring_ref[0],
"event-channel", "%" PRIu32,
&xbb->ring_config.evtchn,
NULL);
if (error != 0) {
xenbus_dev_fatal(xbb->dev, error,
"Unable to retrieve ring information from "
"frontend %s. Unable to connect.",
xenbus_get_otherend_path(xbb->dev));
return (error);
}
/*
* These fields are initialized to legacy protocol defaults
* so we only need to fail if reading the updated value succeeds
* and the new value is outside of its allowed range.
*
* \note xs_gather() returns on the first encountered error, so
* we must use independant calls in order to guarantee
* we don't miss information in a sparsly populated front-end
* tree.
*/
(void)xs_scanf(XST_NIL, otherend_path,
"ring-pages", NULL, "%" PRIu32,
&xbb->ring_config.ring_pages);
(void)xs_scanf(XST_NIL, otherend_path,
"max-requests", NULL, "%" PRIu32,
&xbb->max_requests);
(void)xs_scanf(XST_NIL, otherend_path,
"max-request-segments", NULL, "%" PRIu32,
&xbb->max_request_segments);
(void)xs_scanf(XST_NIL, otherend_path,
"max-request-size", NULL, "%" PRIu32,
&xbb->max_request_size);
if (xbb->ring_config.ring_pages > XBB_MAX_RING_PAGES) {
xenbus_dev_fatal(xbb->dev, EINVAL,
"Front-end specificed ring-pages of %u "
"exceeds backend limit of %zu. "
"Unable to connect.",
xbb->ring_config.ring_pages,
XBB_MAX_RING_PAGES);
return (EINVAL);
} else if (xbb->max_requests > XBB_MAX_REQUESTS) {
xenbus_dev_fatal(xbb->dev, EINVAL,
"Front-end specificed max_requests of %u "
"exceeds backend limit of %u. "
"Unable to connect.",
xbb->max_requests,
XBB_MAX_REQUESTS);
return (EINVAL);
} else if (xbb->max_request_segments > XBB_MAX_SEGMENTS_PER_REQUEST) {
xenbus_dev_fatal(xbb->dev, EINVAL,
"Front-end specificed max_requests_segments "
"of %u exceeds backend limit of %u. "
"Unable to connect.",
xbb->max_request_segments,
XBB_MAX_SEGMENTS_PER_REQUEST);
return (EINVAL);
} else if (xbb->max_request_size > XBB_MAX_REQUEST_SIZE) {
xenbus_dev_fatal(xbb->dev, EINVAL,
"Front-end specificed max_request_size "
"of %u exceeds backend limit of %u. "
"Unable to connect.",
xbb->max_request_size,
XBB_MAX_REQUEST_SIZE);
return (EINVAL);
}
/* If using a multi-page ring, pull in the remaining references. */
for (ring_idx = 1; ring_idx < xbb->ring_config.ring_pages; ring_idx++) {
char ring_ref_name[]= "ring_refXX";
snprintf(ring_ref_name, sizeof(ring_ref_name),
"ring-ref%u", ring_idx);
error = xs_scanf(XST_NIL, otherend_path,
ring_ref_name, NULL, "%" PRIu32,
&xbb->ring_config.ring_ref[ring_idx]);
if (error != 0) {
xenbus_dev_fatal(xbb->dev, error,
"Failed to retriev grant reference "
"for page %u of shared ring. Unable "
"to connect.", ring_idx);
return (error);
}
}
error = xs_gather(XST_NIL, otherend_path,
"protocol", "%63s", protocol_abi,
NULL);
if (error != 0
|| !strcmp(protocol_abi, XEN_IO_PROTO_ABI_NATIVE)) {
/*
* Assume native if the frontend has not
* published ABI data or it has published and
* matches our own ABI.
*/
xbb->abi = BLKIF_PROTOCOL_NATIVE;
} else if (!strcmp(protocol_abi, XEN_IO_PROTO_ABI_X86_32)) {
xbb->abi = BLKIF_PROTOCOL_X86_32;
} else if (!strcmp(protocol_abi, XEN_IO_PROTO_ABI_X86_64)) {
xbb->abi = BLKIF_PROTOCOL_X86_64;
} else {
xenbus_dev_fatal(xbb->dev, EINVAL,
"Unknown protocol ABI (%s) published by "
"frontend. Unable to connect.", protocol_abi);
return (EINVAL);
}
return (0);
}
/**
* Allocate per-request data structures given request size and number
* information negotiated with the front-end.
*
* \param xbb Per-instance xbb configuration structure.
*/
static int
xbb_alloc_requests(struct xbb_softc *xbb)
{
struct xbb_xen_req *req;
struct xbb_xen_req *last_req;
uint8_t *req_kva;
u_long gnt_base;
/*
* Allocate request book keeping datastructures.
*/
xbb->requests = malloc(xbb->max_requests * sizeof(*xbb->requests),
M_XENBLOCKBACK, M_NOWAIT|M_ZERO);
if (xbb->requests == NULL) {
xenbus_dev_fatal(xbb->dev, ENOMEM,
"Unable to allocate request structures");
return (ENOMEM);
}
req_kva = (uint8_t *)xbb->kva;
gnt_base = xbb->gnt_base_addr;
req = xbb->requests;
last_req = &xbb->requests[xbb->max_requests - 1];
while (req <= last_req) {
int seg;
req->xbb = xbb;
req->kva = req_kva;
req->gnt_handles = malloc(xbb->max_request_segments
* sizeof(*req->gnt_handles),
M_XENBLOCKBACK, M_NOWAIT|M_ZERO);
if (req->gnt_handles == NULL) {
xenbus_dev_fatal(xbb->dev, ENOMEM,
"Unable to allocate request "
"grant references");
return (ENOMEM);
}
#ifdef XBB_USE_BOUNCE_BUFFERS
req->bounce = malloc(xbb->max_request_size,
M_XENBLOCKBACK, M_NOWAIT);
if (req->bounce == NULL) {
xenbus_dev_fatal(xbb->dev, ENOMEM,
"Unable to allocate request "
"bounce buffers");
return (ENOMEM);
}
#endif /* XBB_USE_BOUNCE_BUFFERS */
req->gnt_base = gnt_base;
req_kva += xbb->max_request_segments * PAGE_SIZE;
gnt_base += xbb->max_request_segments * PAGE_SIZE;
SLIST_INSERT_HEAD(&xbb->request_free_slist, req, links);
for (seg = 0; seg < xbb->max_request_segments; seg++)
req->gnt_handles[seg] = GRANT_REF_INVALID;
req++;
}
return (0);
}
/**
* Supply information about the physical device to the frontend
* via XenBus.
*
* \param xbb Per-instance xbb configuration structure.
*/
static int
xbb_publish_backend_info(struct xbb_softc *xbb)
{
struct xs_transaction xst;
const char *our_path;
const char *leaf;
int error;
our_path = xenbus_get_node(xbb->dev);
while (1) {
error = xs_transaction_start(&xst);
if (error != 0) {
xenbus_dev_fatal(xbb->dev, error,
"Error publishing backend info "
"(start transaction)");
return (error);
}
leaf = "sectors";
error = xs_printf(xst, our_path, leaf,
"%"PRIu64, xbb->media_num_sectors);
if (error != 0)
break;
/* XXX Support all VBD attributes here. */
leaf = "info";
error = xs_printf(xst, our_path, leaf, "%u",
xbb->flags & XBBF_READ_ONLY
? VDISK_READONLY : 0);
if (error != 0)
break;
leaf = "sector-size";
error = xs_printf(xst, our_path, leaf, "%u",
xbb->sector_size);
if (error != 0)
break;
error = xs_transaction_end(xst, 0);
if (error == 0) {
return (0);
} else if (error != EAGAIN) {
xenbus_dev_fatal(xbb->dev, error, "ending transaction");
return (error);
}
}
xenbus_dev_fatal(xbb->dev, error, "writing %s/%s",
our_path, leaf);
xs_transaction_end(xst, 1);
return (error);
}
/**
* Connect to our blkfront peer now that it has completed publishing
* its configuration into the XenStore.
*
* \param xbb Per-instance xbb configuration structure.
*/
static void
xbb_connect(struct xbb_softc *xbb)
{
int error;
if (xenbus_get_state(xbb->dev) == XenbusStateConnected)
return;
if (xbb_collect_frontend_info(xbb) != 0)
return;
/* Allocate resources whose size depends on front-end configuration. */
error = xbb_alloc_communication_mem(xbb);
if (error != 0) {
xenbus_dev_fatal(xbb->dev, error,
"Unable to allocate communication memory");
return;
}
error = xbb_alloc_requests(xbb);
if (error != 0) {
/* Specific errors are reported by xbb_alloc_requests(). */
return;
}
/*
* Connect communication channel.
*/
error = xbb_connect_ring(xbb);
if (error != 0) {
/* Specific errors are reported by xbb_connect_ring(). */
return;
}
if (xbb_publish_backend_info(xbb) != 0) {
/*
* If we can't publish our data, we cannot participate
* in this connection, and waiting for a front-end state
* change will not help the situation.
*/
xbb_disconnect(xbb);
return;
}
/* Ready for I/O. */
xenbus_set_state(xbb->dev, XenbusStateConnected);
}
/*-------------------------- Device Teardown Support -------------------------*/
/**
* Perform device shutdown functions.
*
* \param xbb Per-instance xbb configuration structure.
*
* Mark this instance as shutting down, wait for any active I/O on the
* backend device/file to drain, disconnect from the front-end, and notify
* any waiters (e.g. a thread invoking our detach method) that detach can
* now proceed.
*/
static int
xbb_shutdown(struct xbb_softc *xbb)
{
static int in_shutdown;
DPRINTF("\n");
/*
* Due to the need to drop our mutex during some
* xenbus operations, it is possible for two threads
* to attempt to close out shutdown processing at
* the same time. Tell the caller that hits this
* race to try back later.
*/
if (in_shutdown != 0)
return (EAGAIN);
DPRINTF("\n");
/* Indicate shutdown is in progress. */
xbb->flags |= XBBF_SHUTDOWN;
/* Wait for requests to complete. */
if (xbb->active_request_count != 0)
return (EAGAIN);
DPRINTF("\n");
/* Disconnect from the front-end. */
xbb_disconnect(xbb);
in_shutdown = 1;
mtx_unlock(&xbb->lock);
xenbus_set_state(xbb->dev, XenbusStateClosed);
mtx_lock(&xbb->lock);
in_shutdown = 0;
/* Indicate to xbb_detach() that is it safe to proceed. */
wakeup(xbb);
return (0);
}
/**
* Report an attach time error to the console and Xen, and cleanup
* this instance by forcing immediate detach processing.
*
* \param xbb Per-instance xbb configuration structure.
* \param err Errno describing the error.
* \param fmt Printf style format and arguments
*/
static void
xbb_attach_failed(struct xbb_softc *xbb, int err, const char *fmt, ...)
{
va_list ap;
va_list ap_hotplug;
va_start(ap, fmt);
va_copy(ap_hotplug, ap);
xs_vprintf(XST_NIL, xenbus_get_node(xbb->dev),
"hotplug-error", fmt, ap_hotplug);
va_end(ap_hotplug);
xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"hotplug-status", "error");
xenbus_dev_vfatal(xbb->dev, err, fmt, ap);
va_end(ap);
xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"online", "0");
xbb_detach(xbb->dev);
}
/*---------------------------- NewBus Entrypoints ----------------------------*/
/**
* Inspect a XenBus device and claim it if is of the appropriate type.
*
* \param dev NewBus device object representing a candidate XenBus device.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_probe(device_t dev)
{
if (!strcmp(xenbus_get_type(dev), "vbd")) {
device_set_desc(dev, "Backend Virtual Block Device");
device_quiet(dev);
return (0);
}
return (ENXIO);
}
/**
* Attach to a XenBus device that has been claimed by our probe routine.
*
* \param dev NewBus device object representing this Xen Block Back instance.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_attach(device_t dev)
{
struct xbb_softc *xbb;
int error;
DPRINTF("Attaching to %s\n", xenbus_get_node(dev));
/*
* Basic initialization.
* After this block it is safe to call xbb_detach()
* to clean up any allocated data for this instance.
*/
xbb = device_get_softc(dev);
xbb->dev = dev;
xbb->otherend_id = xenbus_get_otherend_id(dev);
TASK_INIT(&xbb->io_task, /*priority*/0, xbb_run_queue, xbb);
mtx_init(&xbb->lock, device_get_nameunit(dev), NULL, MTX_DEF);
SLIST_INIT(&xbb->request_free_slist);
/*
* Protocol defaults valid even if all negotiation fails.
*/
xbb->ring_config.ring_pages = 1;
xbb->max_requests = BLKIF_MAX_RING_REQUESTS(PAGE_SIZE);
xbb->max_request_segments = BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK;
xbb->max_request_size = xbb->max_request_segments * PAGE_SIZE;
/*
* Publish protocol capabilities for consumption by the
* front-end.
*/
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"feature-barrier", "1");
if (error) {
xbb_attach_failed(xbb, error, "writing %s/feature-barrier",
xenbus_get_node(xbb->dev));
return (error);
}
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"feature-flush-cache", "1");
if (error) {
xbb_attach_failed(xbb, error, "writing %s/feature-flush-cache",
xenbus_get_node(xbb->dev));
return (error);
}
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"max-ring-pages", "%zu", XBB_MAX_RING_PAGES);
if (error) {
xbb_attach_failed(xbb, error, "writing %s/max-ring-pages",
xenbus_get_node(xbb->dev));
return (error);
}
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"max-requests", "%u", XBB_MAX_REQUESTS);
if (error) {
xbb_attach_failed(xbb, error, "writing %s/max-requests",
xenbus_get_node(xbb->dev));
return (error);
}
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"max-request-segments", "%u",
XBB_MAX_SEGMENTS_PER_REQUEST);
if (error) {
xbb_attach_failed(xbb, error, "writing %s/max-request-segments",
xenbus_get_node(xbb->dev));
return (error);
}
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"max-request-size", "%u",
XBB_MAX_REQUEST_SIZE);
if (error) {
xbb_attach_failed(xbb, error, "writing %s/max-request-size",
xenbus_get_node(xbb->dev));
return (error);
}
/* Collect physical device information. */
error = xs_gather(XST_NIL, xenbus_get_otherend_path(xbb->dev),
"device-type", NULL, &xbb->dev_type,
NULL);
if (error != 0)
xbb->dev_type = NULL;
error = xs_gather(XST_NIL, xenbus_get_node(dev),
"mode", NULL, &xbb->dev_mode,
"params", NULL, &xbb->dev_name,
NULL);
if (error != 0) {
xbb_attach_failed(xbb, error, "reading backend fields at %s",
xenbus_get_node(dev));
return (ENXIO);
}
/* Parse fopen style mode flags. */
if (strchr(xbb->dev_mode, 'w') == NULL)
xbb->flags |= XBBF_READ_ONLY;
/*
* Verify the physical device is present and can support
* the desired I/O mode.
*/
DROP_GIANT();
error = xbb_open_backend(xbb);
PICKUP_GIANT();
if (error != 0) {
xbb_attach_failed(xbb, error, "Unable to open %s",
xbb->dev_name);
return (ENXIO);
}
/* Use devstat(9) for recording statistics. */
xbb->xbb_stats = devstat_new_entry("xbb", device_get_unit(xbb->dev),
xbb->sector_size,
DEVSTAT_ALL_SUPPORTED,
DEVSTAT_TYPE_DIRECT
| DEVSTAT_TYPE_IF_OTHER,
DEVSTAT_PRIORITY_OTHER);
/*
* Create a taskqueue for doing work that must occur from a
* thread context.
*/
xbb->io_taskqueue = taskqueue_create(device_get_nameunit(dev), M_NOWAIT,
taskqueue_thread_enqueue,
/*context*/&xbb->io_taskqueue);
if (xbb->io_taskqueue == NULL) {
xbb_attach_failed(xbb, error, "Unable to create taskqueue");
return (ENOMEM);
}
taskqueue_start_threads(&xbb->io_taskqueue,
/*num threads*/1,
/*priority*/PWAIT,
/*thread name*/
"%s taskq", device_get_nameunit(dev));
/* Update hot-plug status to satisfy xend. */
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"hotplug-status", "connected");
if (error) {
xbb_attach_failed(xbb, error, "writing %s/hotplug-status",
xenbus_get_node(xbb->dev));
return (error);
}
/* Tell the front end that we are ready to connect. */
xenbus_set_state(dev, XenbusStateInitWait);
return (0);
}
/**
* Detach from a block back device instanced.
*
* \param dev NewBus device object representing this Xen Block Back instance.
*
* \return 0 for success, errno codes for failure.
*
* \note A block back device may be detached at any time in its life-cycle,
* including part way through the attach process. For this reason,
* initialization order and the intialization state checks in this
* routine must be carefully coupled so that attach time failures
* are gracefully handled.
*/
static int
xbb_detach(device_t dev)
{
struct xbb_softc *xbb;
DPRINTF("\n");
xbb = device_get_softc(dev);
mtx_lock(&xbb->lock);
while (xbb_shutdown(xbb) == EAGAIN) {
msleep(xbb, &xbb->lock, /*wakeup prio unchanged*/0,
"xbb_shutdown", 0);
}
mtx_unlock(&xbb->lock);
mtx_destroy(&xbb->lock);
DPRINTF("\n");
if (xbb->io_taskqueue != NULL)
taskqueue_free(xbb->io_taskqueue);
if (xbb->xbb_stats != NULL)
devstat_remove_entry(xbb->xbb_stats);
xbb_close_backend(xbb);
xbb_free_communication_mem(xbb);
if (xbb->dev_mode != NULL) {
free(xbb->dev_mode, M_XENBUS);
xbb->dev_mode = NULL;
}
if (xbb->dev_type != NULL) {
free(xbb->dev_type, M_XENBUS);
xbb->dev_type = NULL;
}
if (xbb->dev_name != NULL) {
free(xbb->dev_name, M_XENBUS);
xbb->dev_name = NULL;
}
if (xbb->requests != NULL) {
struct xbb_xen_req *req;
struct xbb_xen_req *last_req;
req = xbb->requests;
last_req = &xbb->requests[xbb->max_requests - 1];
while (req <= last_req) {
#ifdef XBB_USE_BOUNCE_BUFFERS
if (req->bounce != NULL) {
free(req->bounce, M_XENBLOCKBACK);
req->bounce = NULL;
}
#endif
if (req->gnt_handles != NULL) {
free (req->gnt_handles, M_XENBLOCKBACK);
req->gnt_handles = NULL;
}
req++;
}
free(xbb->requests, M_XENBLOCKBACK);
xbb->requests = NULL;
}
return (0);
}
/**
* Prepare this block back device for suspension of this VM.
*
* \param dev NewBus device object representing this Xen Block Back instance.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_suspend(device_t dev)
{
#ifdef NOT_YET
struct xbb_softc *sc = device_get_softc(dev);
/* Prevent new requests being issued until we fix things up. */
mtx_lock(&sc->xb_io_lock);
sc->connected = BLKIF_STATE_SUSPENDED;
mtx_unlock(&sc->xb_io_lock);
#endif
return (0);
}
/**
* Perform any processing required to recover from a suspended state.
*
* \param dev NewBus device object representing this Xen Block Back instance.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_resume(device_t dev)
{
return (0);
}
/**
* Handle state changes expressed via the XenStore by our front-end peer.
*
* \param dev NewBus device object representing this Xen
* Block Back instance.
* \param frontend_state The new state of the front-end.
*
* \return 0 for success, errno codes for failure.
*/
static int
xbb_frontend_changed(device_t dev, XenbusState frontend_state)
{
struct xbb_softc *xbb = device_get_softc(dev);
DPRINTF("state=%s\n", xenbus_strstate(frontend_state));
switch (frontend_state) {
case XenbusStateInitialising:
case XenbusStateClosing:
break;
case XenbusStateInitialised:
case XenbusStateConnected:
xbb_connect(xbb);
break;
case XenbusStateClosed:
case XenbusStateInitWait:
mtx_lock(&xbb->lock);
xbb_shutdown(xbb);
mtx_unlock(&xbb->lock);
break;
default:
xenbus_dev_fatal(xbb->dev, EINVAL, "saw state %d at frontend",
frontend_state);
break;
}
return (0);
}
/*---------------------------- NewBus Registration ---------------------------*/
static device_method_t xbb_methods[] = {
/* Device interface */
DEVMETHOD(device_probe, xbb_probe),
DEVMETHOD(device_attach, xbb_attach),
DEVMETHOD(device_detach, xbb_detach),
DEVMETHOD(device_shutdown, bus_generic_shutdown),
DEVMETHOD(device_suspend, xbb_suspend),
DEVMETHOD(device_resume, xbb_resume),
/* Xenbus interface */
DEVMETHOD(xenbus_otherend_changed, xbb_frontend_changed),
{ 0, 0 }
};
static driver_t xbb_driver = {
"xbbd",
xbb_methods,
sizeof(struct xbb_softc),
};
devclass_t xbb_devclass;
DRIVER_MODULE(xbbd, xenbusb_back, xbb_driver, xbb_devclass, 0, 0);
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