* [PULL 1/2] hw/vfio: Fix liveness check in vfio_connect_kvm_msi_virq()
2026-08-02 13:58 [PULL 0/2] vfio queue Cédric Le Goater
@ 2026-08-02 13:58 ` Cédric Le Goater
2026-08-02 13:58 ` [PULL 2/2] vfio/pci: Guard accel_irqchip_begin_route_changes() calls Cédric Le Goater
2026-08-05 0:54 ` [PULL 0/2] vfio queue Stefan Hajnoczi
2 siblings, 0 replies; 4+ messages in thread
From: Cédric Le Goater @ 2026-08-02 13:58 UTC (permalink / raw)
To: qemu-devel; +Cc: Tycho Andersen (AMD), Cédric Le Goater
From: "Tycho Andersen (AMD)" <tycho@kernel.org>
While working on savevm/loadvm for a new vfio device, I encountered the
crash below. Since vfio_connect_kvm_msi_virq() didn't check the ->use flag
for the vector, it would pass an unused vector down to
vfio_cpr_load_vector_fd() which would crash.
Fix this by checking the ->use flag along with the virq number to detect
whether a vector is valid or not.
Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
0x0000555555a891ef in vfio_cpr_load_vector_fd (vdev=vdev@entry=0x0,
name=name@entry=0x555555eeb27e "kvm_interrupt", nr=nr@entry=1) at ../hw/vfio/cpr.c:44
44 g_autofree char *fdname = STRDUP_VECTOR_FD_NAME(vdev, name);
(gdb) bt
#0 0x0000555555a891ef in vfio_cpr_load_vector_fd
(vdev=vdev@entry=0x0, name=name@entry=0x555555eeb27e "kvm_interrupt", nr=nr@entry=1)
at ../hw/vfio/cpr.c:44
#1 0x0000555555ce64a1 in vfio_notifier_init
(vdev=0x0, e=e@entry=0x5555586971b4, name=name@entry=0x555555eeb27e "kvm_interrupt", nr=nr@entry=1, errp=errp@entry=0x0) at ../hw/vfio/pci.c:79
#2 0x0000555555ce721e in vfio_connect_kvm_msi_virq (vector=0x5555586971a8, nr=nr@entry=1)
at ../hw/vfio/pci.c:601
#3 0x0000555555cea5a5 in vfio_connect_kvm_msi_virq (nr=1, vector=<optimized out>)
at ../hw/vfio/pci.c:597
#4 vfio_pci_commit_kvm_msi_virq_batch (vdev=0x55555906de40) at ../hw/vfio/pci.c:822
#5 0x0000555555cea9f2 in vfio_msix_enable (vdev=vdev@entry=0x55555906de40) at ../hw/vfio/pci.c:850
#6 0x0000555555ceb152 in vfio_pci_load_config (vbasedev=0x55555906e900, f=<optimized out>)
at ../hw/vfio/pci.c:3088
#7 0x0000555555a8c765 in vfio_load_device_config_state (f=0x5555574a43d0, opaque=0x55555906e900)
at ../hw/vfio/migration.c:278
#8 0x0000555555b3a522 in vmstate_load
(f=f@entry=0x5555574a43d0, se=se@entry=0x5555591edd40, errp=errp@entry=0x7fffffffe130)
at ../migration/savevm.c:971
#9 0x0000555555b3ab1a in qemu_loadvm_section_start_full
(f=f@entry=0x5555574a43d0, type=type@entry=4 '\004', errp=errp@entry=0x7fffffffe130)
at ../migration/savevm.c:2654
#10 0x0000555555b3e1ee in qemu_loadvm_state_main
(f=f@entry=0x5555574a43d0, mis=mis@entry=0x5555571de5a0, errp=0x7fffffffe130,
errp@entry=0x555557157c10 <error_fatal>) at ../migration/savevm.c:2973
#11 0x0000555555b3f7b7 in qemu_loadvm_state
(f=f@entry=0x5555574a43d0, errp=errp@entry=0x555557157c10 <error_fatal>)
at ../migration/savevm.c:3058
#12 0x0000555555b40863 in load_snapshot
(name=0x7fffffffecc9 "foo", vmstate=vmstate@entry=0x0, has_devices=has_devices@entry=false, devices=devices@entry=0x0, errp=errp@entry=0x555557157c10 <error_fatal>) at ../migration/savevm.c:3452
#13 0x0000555555adc211 in qmp_x_exit_preconfig (errp=0x555557157c10 <error_fatal>) at ../system/vl.c:2817
#14 qmp_x_exit_preconfig (errp=0x555557157c10 <error_fatal>) at ../system/vl.c:2802
#15 0x0000555555adf8ed in qemu_init (argc=<optimized out>, argv=<optimized out>) at ../system/vl.c:3849
#16 0x00005555558903fd in main (argc=<optimized out>, argv=<optimized out>) at ../system/main.c:71
Fixes: 30edcb4d4e7a ("vfio-pci: preserve MSI")
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260727150038.2684512-1-tycho@kernel.org
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
hw/vfio/pci.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 380dd8c15f8d5bb98b725075978eef2e4e1e6c2d..b5280c3d2a366cd7cff4069936858ac651afeb6d 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -589,7 +589,7 @@ static void vfio_connect_kvm_msi_virq(VFIOMSIVector *vector, int nr)
{
const char *name = "kvm_interrupt";
- if (vector->virq < 0) {
+ if (!vector->use || vector->virq < 0) {
return;
}
--
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PULL 2/2] vfio/pci: Guard accel_irqchip_begin_route_changes() calls
2026-08-02 13:58 [PULL 0/2] vfio queue Cédric Le Goater
2026-08-02 13:58 ` [PULL 1/2] hw/vfio: Fix liveness check in vfio_connect_kvm_msi_virq() Cédric Le Goater
@ 2026-08-02 13:58 ` Cédric Le Goater
2026-08-05 0:54 ` [PULL 0/2] vfio queue Stefan Hajnoczi
2 siblings, 0 replies; 4+ messages in thread
From: Cédric Le Goater @ 2026-08-02 13:58 UTC (permalink / raw)
To: qemu-devel; +Cc: Cédric Le Goater, Magnus Kulke
Since commit 49b2dcbd2422 ("accel/accel-irq: add generic
begin_route_changes"), accel_irqchip_begin_route_changes() aborts when
no accelerator irqchip is available. This causes a fatal error when
running VFIO passthrough devices under TCG emulation:
qemu-system-aarch64: can't initiate route change, no accel irqchip available
The previous kvm_irqchip_begin_route_changes() was a simple inline
that did not have a fatal path. The VFIO code already handles the
absence of KVM MSI routing gracefully by falling back to userspace
handling, but the new generic function aborts before that fallback
can take effect.
Guard the call sites in hw/vfio/pci.c with
accel_msi_via_irqfd_enabled() so that route changes are only
initiated when an accelerator irqchip is actually present.
Fixes: 49b2dcbd2422 ("accel/accel-irq: add generic begin_route_changes")
Cc: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/qemu-devel/20260721105026.3932297-1-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
hw/vfio/pci.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index b5280c3d2a366cd7cff4069936858ac651afeb6d..428ab2f06983ba9ecb306975a4aca7f6efe1b855 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -699,7 +699,7 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
if (msg) {
if (vdev->defer_kvm_irq_routing) {
vfio_pci_add_kvm_msi_virq(vdev, vector, nr, true);
- } else {
+ } else if (accel_msi_via_irqfd_enabled()) {
vfio_route_change = accel_irqchip_begin_route_changes();
vfio_pci_add_kvm_msi_virq(vdev, vector, nr, true);
accel_irqchip_commit_route_changes(&vfio_route_change);
@@ -801,7 +801,9 @@ void vfio_pci_prepare_kvm_msi_virq_batch(VFIOPCIDevice *vdev)
{
assert(!vdev->defer_kvm_irq_routing);
vdev->defer_kvm_irq_routing = true;
- vfio_route_change = accel_irqchip_begin_route_changes();
+ if (accel_msi_via_irqfd_enabled()) {
+ vfio_route_change = accel_irqchip_begin_route_changes();
+ }
}
void vfio_pci_commit_kvm_msi_virq_batch(VFIOPCIDevice *vdev)
--
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread