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Enable I/O MMU when PCI pass through is first used.

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Rather than enabling the I/O MMU when the vmm module is loaded,
defer initialization until the first attempt to pass a PCI device
through to a guest.  If the I/O MMU fails to initialize or is not
present, than fail the attempt to pass a PCI device through to a
guest.

The hw.vmm.force_iommu tunable has been removed since the I/O MMU is
no longer enabled during boot.  However, the I/O MMU support can be
disabled by setting the hw.vmm.iommu.enable tunable to 0 to prevent
use of the I/O MMU on any systems where it is buggy.

Reviewed by:	grehan
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D7448
This commit is contained in:
John Baldwin 2016-08-26 20:15:22 +00:00
parent 06b99bd826
commit ffe1b10d95
3 changed files with 27 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
sys/amd64/vmm/io/iommu.c
View File

@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
#include <dev/pci/pcivar.h>
#include <dev/pci/pcireg.h>
#include <machine/cpu.h>
#include <machine/md_var.h>
#include "vmm_util.h"
@ -51,6 +52,10 @@ static int iommu_avail;
SYSCTL_INT(_hw_vmm_iommu, OID_AUTO, initialized, CTLFLAG_RD, &iommu_avail,
0, "bhyve iommu initialized?");
static int iommu_enable = 1;
SYSCTL_INT(_hw_vmm_iommu, OID_AUTO, enable, CTLFLAG_RDTUN, &iommu_enable, 0,
"Enable use of I/O MMU (required for PCI passthrough).");
static struct iommu_ops *ops;
static void *host_domain;
@ -148,7 +153,7 @@ IOMMU_DISABLE(void)
(*ops->disable)();
}
void
static void
iommu_init(void)
{
int error, bus, slot, func;
@ -156,6 +161,9 @@ iommu_init(void)
const char *name;
device_t dev;
if (!iommu_enable)
return;
if (vmm_is_intel())
ops = &iommu_ops_intel;
else if (vmm_is_amd())
@ -174,8 +182,13 @@ iommu_init(void)
*/
maxaddr = vmm_mem_maxaddr();
host_domain = IOMMU_CREATE_DOMAIN(maxaddr);
if (host_domain == NULL)
panic("iommu_init: unable to create a host domain");
if (host_domain == NULL) {
printf("iommu_init: unable to create a host domain");
IOMMU_CLEANUP();
ops = NULL;
iommu_avail = 0;
return;
}
/*
* Create 1:1 mappings from '0' to 'maxaddr' for devices assigned to
@ -216,7 +229,16 @@ iommu_cleanup(void)
void *
iommu_create_domain(vm_paddr_t maxaddr)
{
static volatile int iommu_initted;
if (iommu_initted < 2) {
if (atomic_cmpset_int(&iommu_initted, 0, 1)) {
iommu_init();
atomic_store_rel_int(&iommu_initted, 2);
} else
while (iommu_initted == 1)
cpu_spinwait();
}
return (IOMMU_CREATE_DOMAIN(maxaddr));
}

1
sys/amd64/vmm/io/iommu.h
View File

@ -61,7 +61,6 @@ struct iommu_ops {
extern struct iommu_ops iommu_ops_intel;
extern struct iommu_ops iommu_ops_amd;
void iommu_init(void);
void iommu_cleanup(void);
void *iommu_host_domain(void);
void *iommu_create_domain(vm_paddr_t maxaddr);

12
sys/amd64/vmm/vmm.c
View File

@ -224,11 +224,6 @@ SYSCTL_INT(_hw_vmm, OID_AUTO, trace_guest_exceptions, CTLFLAG_RDTUN,
&trace_guest_exceptions, 0,
"Trap into hypervisor on all guest exceptions and reflect them back");
static int vmm_force_iommu = 0;
TUNABLE_INT("hw.vmm.force_iommu", &vmm_force_iommu);
SYSCTL_INT(_hw_vmm, OID_AUTO, force_iommu, CTLFLAG_RDTUN, &vmm_force_iommu, 0,
"Force use of I/O MMU even if no passthrough devices were found.");
static void vm_free_memmap(struct vm *vm, int ident);
static bool sysmem_mapping(struct vm *vm, struct mem_map *mm);
static void vcpu_notify_event_locked(struct vcpu *vcpu, bool lapic_intr);
@ -358,8 +353,6 @@ vmm_handler(module_t mod, int what, void *arg)
switch (what) {
case MOD_LOAD:
vmmdev_init();
if (vmm_force_iommu || ppt_avail_devices() > 0)
iommu_init();
error = vmm_init();
if (error == 0)
vmm_initialized = 1;
@ -396,9 +389,6 @@ static moduledata_t vmm_kmod = {
/*
* vmm initialization has the following dependencies:
*
* - iommu initialization must happen after the pci passthru driver has had
* a chance to attach to any passthru devices (after SI_SUB_CONFIGURE).
*
* - VT-x initialization requires smp_rendezvous() and therefore must happen
* after SMP is fully functional (after SI_SUB_SMP).
*/
@ -893,6 +883,8 @@ vm_assign_pptdev(struct vm *vm, int bus, int slot, int func)
("vm_assign_pptdev: iommu must be NULL"));
maxaddr = sysmem_maxaddr(vm);
vm->iommu = iommu_create_domain(maxaddr);
if (vm->iommu == NULL)
return (ENXIO);
vm_iommu_map(vm);
}