Commit Graph

131 Commits

Author SHA1 Message Date
Roger Pau Monné
50d7d967bb xen/privcmd: fix MMAP_RESOURCE ioctl to copy out results
The current definition for the MMAP_RESOURCE ioctl was wrong as it
didn't copy back the result to the caller. Fix the definition and also
remove the bogus attempt to copy the result in the implementation.

Note such copy back is only needed when querying the size of a
resource.

Sponsored by: Citrix Systems R&D
2021-11-18 09:46:44 +01:00
Julien Grall
69c6eee756 xen: introduce xen_pv_disks_disabled()
ARM guest is considered as HVM in Freebsd but they only support PV disk
(no emulation available).

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D29403
2021-07-28 17:27:04 +02:00
Julien Grall
5f70008327 xen/netfront: introduce xen_pv_nics_disabled()
ARM guest is considered as HVM but it only supports PV nics (no
emulation available).

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D29405
2021-07-28 17:27:04 +02:00
Elliott Mitchell
c89f1f12b0 xen/xen-os: move inclusion of machine/xen-os.h later
Several of x86 enable/disable functions depend upon the xen*domain()
functions.  As such the xen*domain() functions need to be declared
before machine/xen-os.h.

Officially declare direct inclusion of machine/xen/xen-os.h verboten as
such will break these functions/macros.  Remove one such soon to be
broken inclusion.

Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D29811
2021-07-28 17:27:04 +02:00
Julien Grall
d561380eb3 xen/xen-os: don't let anyone else defining __XEN_INTERFACE_VERSION__
FreeBSD should always use the same version across the source. If not
it's a call for problem.

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D29407
2021-07-28 17:27:02 +02:00
Roger Pau Monné
ac3ede5371 x86/xen: remove PVHv1 code
PVHv1 was officially removed from Xen in 4.9, so just axe the related
code from FreeBSD.

Note FreeBSD supports PVHv2, which is the replacement for PVHv1.

Sponsored by: Citrix Systems R&D
Reviewed by: kib, Elliott Mitchell
Differential Revision: https://reviews.freebsd.org/D30228
2021-05-17 11:41:21 +02:00
Mitchell Horne
2117a66af5 xen: remove hypervisor_info
This was a source of indirection needed to support PVHv1. Now that that
support has been removed, we can eliminate it.

Reviewed by: royger
2021-05-17 10:56:52 +02:00
Julien Grall
b55c0d5f56 xen: move x86-specific xen_vector_callback_enabled to sys/x86
This is x86-only and so should not be in the common area.

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential revision: https://reviews.freebsd.org/D29040
2021-03-15 14:20:21 +01:00
Julien Grall
ff5272ca71 xen/xenusb: always include xen/xen-os.h rather than machine/xen/xen-os.h
Fix compilation since machine/xen/xen-os.h is requiring definition
existing in xen/xen-os.h.

In general machine/xen/xen-os.h should never be included

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential revision: https://reviews.freebsd.org/D29043
2021-03-15 14:20:21 +01:00
Roger Pau Monné
d1eb05aa0c xen: remove .swp file from public headers
Should have never been there in the first place.
2021-01-11 18:14:11 +01:00
Roger Pau Monne
a765078790 xen/privcmd: implement the restrict ioctl
Use an interface compatible with the Linux one so that the user-space
libraries already using the Linux interface can be used without much
modifications.

This allows an open privcmd instance to limit against which domains it
can act upon.

Sponsored by:	Citrix Systems R&D
2021-01-11 16:33:27 +01:00
Roger Pau Monne
ed78016d00 xen/privcmd: implement the dm op ioctl
Use an interface compatible with the Linux one so that the user-space
libraries already using the Linux interface can be used without much
modifications.

This allows user-space to make use of the dm_op family of hypercalls,
which are used by device models.

Sponsored by:	Citrix Systems R&D
2021-01-11 16:33:27 +01:00
Roger Pau Monne
658860e2d0 xen/privcmd: implement the map resource ioctl
The interface is mostly the same as the Linux ioctl, so that we don't
need to modify the user-space libraries that make use of it.

The ioctl is just a proxy for the XENMEM_acquire_resource hypercall.

Sponsored by:	Citrix Systems R&D
2021-01-11 16:15:00 +01:00
Roger Pau Monné
5ed9deef6b xen: update interface headers
This is a verbatim copy of the public headers from Xen 4.14.1.

No functional change intended.

Sponsored by: Citrix Systems R&D
2021-01-11 16:14:59 +01:00
Roger Pau Monné
4e4e43dc9e xen: allow limiting the amount of duplicated pending xenstore watches
Xenstore watches received are queued in a list and processed in a
deferred thread. Such queuing was done without any checking, so a
guest could potentially trigger a resource starvation against the
FreeBSD kernel if such kernel is watching any user-controlled xenstore
path.

Allowing limiting the amount of pending events a watch can accumulate
to prevent a remote guest from triggering this resource starvation
issue.

For the PV device backends and frontends this limitation is only
applied to the other end /state node, which is limited to 1 pending
event, the rest of the watched paths can still have unlimited pending
watches because they are either local or controlled by a privileged
domain.

The xenstore user-space device gets special treatment as it's not
possible for the kernel to know whether the paths being watched by
user-space processes are controlled by a guest domain. For this reason
watches set by the xenstore user-space device are limited to 1000
pending events. Note this can be modified using the
max_pending_watch_events sysctl of the device.

This is XSA-349.

Sponsored by:	Citrix Systems R&D
MFC after:	3 days
2020-12-30 11:18:26 +01:00
Roger Pau Monné
2ae75536d3 xen/xenstore: remove unused functions
Those helpers are not used, so remove them. No functional change.

Sponsored by:	Citrix Systems R&D
MFC after:	3 days
2020-12-30 11:18:25 +01:00
Mateusz Guzik
59958e948c xen: clean up empty lines in .c and .h files 2020-09-01 21:21:55 +00:00
Pawel Biernacki
41fc1ce14c Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (16 of many)
r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all obvious cases as MPSAFE.

Reviewed by:	royger
Approved by:	kib (mentor, blanket)
Differential Revision:	https://reviews.freebsd.org/D23638
2020-02-25 19:04:39 +00:00
Roger Pau Monné
27c36a12f1 xen: introduce a new way to setup event channel upcall
The main differences with the currently implemented method are:

 - Requires a local APIC EOI, since it doesn't bypass the local APIC
   as the previous method used to do.
 - Can be set to use different IDT vectors on each vCPU. Note that
   FreeBSD doesn't make use of this feature since the event channel
   IDT vector is reserved system wide.

Note that the old method of setting the event channel upcall is
not removed, and will be used as a fallback if this newly introduced
method is not available.

MFC after:	1 month
Sponsored by:	Citrix Systems R&D
2019-01-30 11:34:52 +00:00
Roger Pau Monné
a74cdf4e74 xen: legacy PVH fixes for the new interrupt count
Register interrupts using the PIC pic_register_sources method instead
of doing it in apic_setup_io. This is now required, since the internal
interrupt structures are not yet setup when calling apic_setup_io.

Approved by:		re (gjb)
Sponsored by:		Citrix Systems R&D
2018-09-13 07:14:11 +00:00
Roger Pau Monné
b21c72b69d xen: add missing file from r336474 2018-07-19 10:14:52 +00:00
Roger Pau Monné
b0663c33c2 xen: implement early init helper for PVHv2
In order to setup an initial environment and jump into the generic
hammer_time initialization function. Some of the code is shared with
PVHv1, while other code is PVHv2 specific.

This allows booting FreeBSD as a PVHv2 DomU and Dom0.

Sponsored by:	Citrix Systems R&D
2018-07-19 08:44:52 +00:00
Roger Pau Monné
07c2711fbf xen: allow very early initialization of the hypercall page
Allow the hypercall page to be initialized very early, even before
vtophys is functional. Also make the function global so it can be
called by other files.

This will be needed in order to perform the early bringup on PVHv2
guests.

Sponsored by: Citrix Systems R&D
2018-07-19 08:13:41 +00:00
Roger Pau Monné
cfa0b7b82f xen: remove direct usage of HYPERVISOR_start_info
HYPERVISOR_start_info is only available to PV and PVHv1 guests, HVM
and PVHv2 guests get this data from HVM parameters that are fetched
using a hypercall.

Instead provide a set of helper functions that should be used to fetch
this data. The helper functions have different implementations
depending on whether FreeBSD is running as PVHv1 or HVM/PVHv2 guest
type.

This helps to cleanup generic Xen code by removing quite a lot of
xen_pv_domain and xen_hvm_domain macro usages.

Sponsored by:	Citrix Systems R&D
2018-07-19 07:54:45 +00:00
Roger Pau Monné
f2577f25c1 xen: add PVHv2 entry point
The PVHv2 entry point is fairly similar to the multiboot1 one. The
kernel is started in protected mode with paging disabled. More
information about the exact BSP state can be found in the pvh.markdown
document on the Xen tree.

This entry point is going to be joined with the native entry point at
hammer_time, and in order to do so the BSP needs to be bootstrapped
into long mode with the same set of page tables as used on bare metal.

Sponsored by:	Citrix Systems R&D
2018-07-19 07:39:35 +00:00
Roger Pau Monné
69ec6041d2 xen: remove dead code from gnttab.h
This code was left over when it was imported from Linux. The original
committer thought that those functions would be implemented, so the
prototypes where left in place. Delete them at once.

Submitted by:		pratyush
Reviewed by:		royger
Differential Review:	https://reviews.freebsd.org/D15553
2018-05-25 08:44:00 +00:00
Roger Pau Monné
2602ef7cfa xen: fix gntdev
Current interface to the gntdev in FreeBSD is wrong, and mostly worked
out of luck before the PTI FreeBSD fixes, when kernel and user-space
where sharing the same page tables.

On FreeBSD ioctls have the size of the passed struct encoded in the
ioctl number, because the generic ioctl handler in the OS takes care
of copying the data from user-space to kernel space, and then calls
the device specific ioctl handler. Thus using ioctl structs with
variable sizes is not possible.

The fix is to turn the array of structs at the end of
ioctl_gntdev_alloc_gref and ioctl_gntdev_map_grant_ref into pointers,
that can be properly accessed from the kernel gntdev driver using the
copyin/copyout functions. Note that this is exactly how it's done for
the privcmd driver.

Sponsored by:   Citrix Systems R&D
2018-05-02 10:19:17 +00:00
Pedro F. Giffuni
fe267a5590 sys: general adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.
2017-11-27 15:23:17 +00:00
Roger Pau Monné
41716b8d51 xenstore: fix suspension when using the xenstore device
Lock the xenstore request mutex when suspending user-space processes, in order
to prevent any process from holding this lock when going into suspension, or
else the xenstore suspend process is going to deadlock.

Submitted by:		Liuyingdong <liuyingdong@huawei.com>
Reviewed by:		royger
MFC after:		2 weeks
Differential revision:	https://reviews.freebsd.org/D9638
2017-03-07 09:17:48 +00:00
Roger Pau Monné
8dee0e9bd6 xen: add support for canceled suspend
When running on Xen, it's possible that a suspend request to the hypervisor
fails (return from HYPERVISOR_suspend different than 0). This means that the
suspend hasn't succeed, and the resume procedure needs to properly handle this
case.

First of all, when such situation happens there's no need to reset the vector
callback, hypercall page, shared info, event channels or grant table, because
it's state is preserved. Also, the PV drivers don't need to be reset to the
initial state, since the connection with the backed has not been interrupted.

Submitted by:		Liuyingdong <liuyingdong@huawei.com>
Reviewed by:		royger
MFC after:		2 weeks
Differential revision:	https://reviews.freebsd.org/D9635
2017-03-07 09:16:51 +00:00
Conrad Meyer
db4fcadf52 "Buses" is the preferred plural of "bus"
Replace archaic "busses" with modern form "buses."

Intentionally excluded:
* Old/random drivers I didn't recognize
  * Old hardware in general
* Use of "busses" in code as identifiers

No functional change.

http://grammarist.com/spelling/buses-busses/

PR:		216099
Reported by:	bltsrc at mail.ru
Sponsored by:	Dell EMC Isilon
2017-01-15 17:54:01 +00:00
Roger Pau Monné
ca7af67ac9 xen: fix IPI setup with EARLY_AP_STARTUP
Current Xen IPI setup functions require that the caller provide a device in
order to obtain the name of the interrupt from it. With early AP startup this
device is no longer available at the point where IPIs are bound, and a KASSERT
would trigger:

panic: NULL pcpu device_t
cpuid = 0
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xffffffff82233a20
vpanic() at vpanic+0x186/frame 0xffffffff82233aa0
kassert_panic() at kassert_panic+0x126/frame 0xffffffff82233b10
xen_setup_cpus() at xen_setup_cpus+0x5b/frame 0xffffffff82233b50
mi_startup() at mi_startup+0x118/frame 0xffffffff82233b70
btext() at btext+0x2c

Fix this by no longer requiring the presence of a device in order to bind IPIs,
and simply use the "cpuX" format where X is the CPU identifier in order to
describe the interrupt.

Reported by:            sbruno, cperciva
Tested by:              sbruno
X-MFC-With:             r310177
Sponsored by:           Citrix Systems R&D
2016-12-22 16:09:44 +00:00
Roger Pau Monné
78eb32933b xen: add a grant-table user-space device
A grant-table user-space device will allow user-space applications to map
and share grants (Xen way to share memory) among Xen domains. This grant
table user-space device has been tested with the QEMU Qdisk Xen backed.

Submitted by:		jaggi
Reviewed by:		royger
Differential review:	https://reviews.freebsd.org/D7293
2016-10-31 13:12:58 +00:00
Roger Pau Monné
0f4d7d9fd7 xen/intr: add reference counts to event channels
Add a reference count to xenisrc. This is required for implementation of
unmap-notifications in the grant table userspace device (gntdev). We need to
hold a reference to the event channel port, in case the user deallocates the
port before we send the notification.

Submitted by:		jaggi
Reviewed by:		royger
Differential review:	https://reviews.freebsd.org/D7429
2016-10-31 13:00:53 +00:00
Roger Pau Monné
7f510c8f01 xen/vchan: change license of header from Lesser GPL v2.1 to BSD
This is a license change only commit, which can be found upstream in the Xen
tree as 937324f032f4f77866e80e39de0d697fa5131df1.

Sponsored by: Citrix Systems R&D
2016-09-30 13:41:24 +00:00
Roger Pau Monné
89ee6cecbc xen: Correct typo in #undef for symbol NBPL
Submitted by:	Akshay Jaggi <akshay1994.leo@gmail.com>
Reviewed by:	royger
2016-06-06 14:55:46 +00:00
Roger Pau Monné
7b1d3a09e3 xen: rewrite Xen error translation
Using the public Xen error code header.

Submitted by:	Akshay Jaggi <akshay1994.leo@gmail.com>
Reviewed by:	royger
2016-06-02 07:45:01 +00:00
Roger Pau Monné
71da5f7a01 xen: add missing #define in include guard.
Submitted by:	Akshay Jaggi <akshay1994.leo@gmail.com>
Reviewed by:	royger
2016-06-02 07:43:02 +00:00
Eitan Adler
cef367e6a1 Don't repeat the the word 'the'
(one manual change to fix grammar)

Confirmed With: db
Approved by: secteam (not really, but this is a comment typo fix)
2016-05-17 12:52:31 +00:00
Roger Pau Monné
137c69ea60 xenbus: add a comment with the names of the generated accessors
For easy grepping.

Sponsored by:		Citrix Systems R&D
2016-01-15 14:34:31 +00:00
Marcelo Araujo
f7e124adf5 Clean up unused-but-set-variable spotted by gcc-4.9.
Reviewed by:	royger
Approved by:	rodrigc (mentor)
Differential Revision:	https://reviews.freebsd.org/D4733
2015-12-31 01:54:07 +00:00
Roger Pau Monné
f186ed526a xen/intr: fix the event channel enabled per-cpu mask
Fix two issues with the current event channel code, first ENABLED_SETSIZE is
not correctly defined and then using a BITSET to store the per-cpu masks is
not portable to other arches, since on arm32 the event channel arrays shared
with the hypervisor are of type uint64_t and not long. Partially restore the
previous code but switch the bit operations to use the recently introduced
xen_{set/clear/test}_bit versions.

Reviewed by:		Julien Grall <julien.grall@citrix.com>
Sponsored by:		Citrix Systems R&D
Differential Revision:	https://reviews.freebsd.org/D4080
2015-11-05 14:33:46 +00:00
Roger Pau Monné
2f9ec994bc xen: Code cleanup and small bug fixes
xen/hypervisor.h:
 - Remove unused helpers: MULTI_update_va_mapping, is_initial_xendomain,
   is_running_on_xen
 - Remove unused define CONFIG_X86_PAE
 - Remove unused variable xen_start_info: note that it's used inpcifront
   which is not built at all
 - Remove forward declaration of HYPERVISOR_crash

xen/xen-os.h:
 - Remove unused define CONFIG_X86_PAE
 - Drop unused helpers: test_and_clear_bit, clear_bit,
   force_evtchn_callback
 - Implement a generic version (based on ofed/include/linux/bitops.h) of
   set_bit and test_bit and prefix them by xen_ to avoid any use by other
   code than Xen. Note that It would be worth to investigate a generic
   implementation in FreeBSD.
 - Replace barrier() by __compiler_membar()
 - Replace cpu_relax() by cpu_spinwait(): it's exactly the same as rep;nop
   = pause

xen/xen_intr.h:
 - Move the prototype of xen_intr_handle_upcall in it: Use by all the
   platform

x86/xen/xen_intr.c:
 - Use BITSET* for the enabledbits: Avoid to use custom helpers
 - test_bit/set_bit has been renamed to xen_test_bit/xen_set_bit
 - Don't export the variable xen_intr_pcpu

dev/xen/blkback/blkback.c:
 - Fix the string format when XBB_DEBUG is enabled: host_addr is typed
   uint64_t

dev/xen/balloon/balloon.c:
 - Remove set but not used variable
 - Use the correct type for frame_list: xen_pfn_t represents the frame
   number on any architecture

dev/xen/control/control.c:
 - Return BUS_PROBE_WILDCARD in xs_probe: Returning 0 in a probe callback
   means the driver can handle this device. If by any chance xenstore is the
   first driver, every new device with the driver is unset will use
   xenstore.

dev/xen/grant-table/grant_table.c:
 - Remove unused cmpxchg
 - Drop unused include opt_pmap.h: Doesn't exist on ARM64 and it doesn't
   contain anything required for the code on x86

dev/xen/netfront/netfront.c:
 - Use the correct type for rx_pfn_array: xen_pfn_t represents the frame
   number on any architecture

dev/xen/netback/netback.c:
 - Use the correct type for gmfn: xen_pfn_t represents the frame number on
   any architecture

dev/xen/xenstore/xenstore.c:
 - Return BUS_PROBE_WILDCARD in xctrl_probe: Returning 0 in a probe callback
   means the driver can handle this device. If by any chance xenstore is the
  first driver, every new device with the driver is unset will use xenstore.

Note that with the changes, x86/include/xen/xen-os.h doesn't contain anymore
arch-specific code. Although, a new series will add some helpers that differ
between x86 and ARM64, so I've kept the headers for now.

Submitted by:		Julien Grall <julien.grall@citrix.com>
Reviewed by:		royger
Differential Revision:	https://reviews.freebsd.org/D3921
Sponsored by:		Citrix Systems R&D
2015-10-21 10:44:07 +00:00
Roger Pau Monné
a231723cc0 xen/console: Introduce a new console driver for Xen guest
The current Xen console driver is crashing very quickly when using it on
an ARM guest. This is because the console lock is recursive and it may
lead to recursion on the tty lock and/or corrupt the ring pointer.

Furthermore, the console lock is not always taken where it should be and has
to be released too early because of the way the console has been designed.

Over the years, code has been modified to support various new features but
the driver has not been reworked.

This new driver has been rewritten with the idea of only having a small set
of specific function to write either via the shared ring or the hypercall
interface.

Note that HVM support has been left aside for now because it requires
additional features which are not yet supported. A follow-up patch will be
sent with HVM guest support.

List of items that may be good to have but not mandatory:
 - Avoid to flush for each character written when using the tty
 - Support multiple consoles

Submitted by:		Julien Grall <julien.grall@citrix.com>
Reviewed by:		royger
Differential Revision:	https://reviews.freebsd.org/D3698
Sponsored by:		Citrix Systems R&D
2015-10-08 16:39:43 +00:00
Roger Pau Monné
1a52c10530 Update Xen headers from 4.2 to 4.6
Pull the latest headers for Xen which allow us to add support for ARM and
use new features in FreeBSD.

This is a verbatim copy of the xen/include/public so every headers which
don't exits anymore in the Xen repositories have been dropped.

Note the interface version hasn't been bumped, it will be done in a
follow-up. Although, it requires fix in the code to get it compiled:

 - sys/xen/xen_intr.h: evtchn_port_t is already defined in the headers so
   drop it.

 - {amd64,i386}/include/intr_machdep.h: NR_EVENT_CHANNELS now depends on
   xen/interface/event_channel.h, so include it.

 - {amd64,i386}/{amd64,i386}/support.S: It's not neccessary to include
   machine/intr_machdep.h. This is also fixing build compilation with the
   new headers.

 - dev/xen/blkfront/blkfront.c: The typedef for blkif_request_segmenthas
   been dropped. So directly use struct blkif_request_segment

Finally, modify xen/interface/xen-compat.h to throw a preprocessing error if
__XEN_INTERFACE_VERSION__ is not set. This is allow us to catch any file
where xen/xen-os.h is not correctly included.

Submitted by:		Julien Grall <julien.grall@citrix.com>
Reviewed by:		royger
Differential Revision:	https://reviews.freebsd.org/D3805
Sponsored by:		Citrix Systems R&D
2015-10-06 11:29:44 +00:00
Roger Pau Monné
f8f1bb83f7 xen: allow disabling PV disks and nics
Introduce two new loader tunnables that can be used to disable PV disks and
PV nics at boot time. They default to 0 and should be set to 1 (or any
number different than 0) in order to disable the PV devices:

hw.xen.disable_pv_disks=1
hw.xen.disable_pv_nics=1

In /boot/loader.conf will disable both PV disks and nics.

Sponsored by:	Citrix Systems R&D
Tested by:	Karl Pielorz <kpielorz_lst@tdx.co.uk>
MFC after:	1 week
2015-08-21 15:53:08 +00:00
John Baldwin
3ebe4c01f7 Remove another remnant of PV domU support and assume that we always run
with an automatically translated physmap under XEN.

Reviewed by:	royger (earlier version)
Differential Revision:	https://reviews.freebsd.org/D3325
2015-08-14 18:38:39 +00:00
Colin Percival
aaebf69062 Add support for Xen blkif indirect segment I/Os. This makes it possible for
the blkfront driver to perform I/Os of up to 2 MB, subject to support from
the blkback to which it is connected and the initiation of such large I/Os
by the rest of the kernel.  In practice, the I/O size is increased from 40 kB
to 128 kB.

The changes to xen/interface/io/blkif.h consist merely of merging updates
from the upstream Xen repository.

In dev/xen/blkfront/block.h we add some convenience macros and structure
fields used for indirect-page I/Os: The device records its negotiated limit
on the number of indirect pages used, while each I/O command structure gains
permanently allocated page(s) for indirect page references and the Xen grant
references for those pages.

In dev/xen/blkfront/blkfront.c we now check in xbd_queue_cb whether a request
is small enough to handle without an indirection page, and either follow the
previous behaviour or use new code for issuing an indirect segment I/O.  In
xbd_connect we read the size of indirect segment I/Os supported by the backend
and select the maximum size we will use; then allocate the pages and Xen grant
references for each I/O command structure.  In xbd_free those grants and pages
are released.

A new loader tunable, hw.xbd.xbd_enable_indirect, can be set to 0 in order to
disable this functionality; it works by pretending that the backend does not
support this feature.  Some backends exhibit a loss of performance with large
I/Os, so users may wish to test with and without this functionality enabled.

Reviewed by:	royger
MFC after:	3 days
Relnotes:	yes
2015-07-30 03:50:01 +00:00
Colin Percival
c077dc26e7 Garbage collect comments which related to the pre-r284296 support for a
"segment block" extension in FreeBSD's Xen blkfront/blkback drivers.

Since this commit only affects comments, it should have no functional
effect.
2015-06-21 06:05:33 +00:00
Roger Pau Monné
112cacaee4 xen-blk{front/back}: remove broken FreeBSD extensions
The FreeBSD extension adds a new request type, called blkif_segment_block
which has a size of 112bytes for both i386 and amd64. This is fine on
amd64, since requests have a size of 112B there also. But this is not true
for i386, where requests have a size of 108B. So on i386 we basically
overrun the ring slot when queuing a request of type blkif_segment_block_t,
which is very bad.

Remove this extension (including a cleanup of the public blkif.h header
file) from blkfront and blkback.

Sponsored by: Citrix Systems R&D
Tested-by: cperciva
2015-06-12 07:50:34 +00:00