During the booting process of the non-standard image, the behavior of the
called function in qemu is as follows:

1. vhost_net_stop() was triggered by guest image. This will call the function
virtio_pci_set_guest_notifiers() with assgin= false,
virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0

2. virtio_reset() was triggered, this will set configure vector to VIRTIO_NO_VECTOR

3.vhost_net_start() was called (at this time, the configure vector is
still VIRTIO_NO_VECTOR) and then call virtio_pci_set_guest_notifiers() with
assgin=true, so the irqfd for vector 0 is still not "init" during this process

4. The system continues to boot and sets the vector back to 0. After that
msix_fire_vector_notifier() was triggered to unmask the vector 0 and  meet the crash

To fix the issue, we need to support changing the vector after VIRTIO_CONFIG_S_DRIVER_OK is set.

(gdb) bt
0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0)
    at pthread_kill.c:44
1  0x00007fc87148ec53 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
2  0x00007fc87143e956 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
3  0x00007fc8714287f4 in __GI_abort () at abort.c:79
4  0x00007fc87142871b in __assert_fail_base
    (fmt=0x7fc8715bbde0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=<optimized out>) at assert.c:92
5  0x00007fc871437536 in __GI___assert_fail
    (assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=0x5606413f06f0 <__PRETTY_FUNCTION__.19> "kvm_irqchip_commit_routes") at assert.c:101
6  0x0000560640f884b5 in kvm_irqchip_commit_routes (s=0x560642cae1f0) at ../accel/kvm/kvm-all.c:1837
7  0x0000560640c98f8e in virtio_pci_one_vector_unmask
    (proxy=0x560643c65f00, queue_no=4294967295, vector=0, msg=..., n=0x560643c6e4c8)
    at ../hw/virtio/virtio-pci.c:1005
8  0x0000560640c99201 in virtio_pci_vector_unmask (dev=0x560643c65f00, vector=0, msg=...)
    at ../hw/virtio/virtio-pci.c:1070
9  0x0000560640bc402e in msix_fire_vector_notifier (dev=0x560643c65f00, vector=0, is_masked=false)
    at ../hw/pci/msix.c:120
10 0x0000560640bc40f1 in msix_handle_mask_update (dev=0x560643c65f00, vector=0, was_masked=true)
    at ../hw/pci/msix.c:140
11 0x0000560640bc4503 in msix_table_mmio_write (opaque=0x560643c65f00, addr=12, val=0, size=4)
    at ../hw/pci/msix.c:231
12 0x0000560640f26d83 in memory_region_write_accessor
    (mr=0x560643c66540, addr=12, value=0x7fc86b7bc628, size=4, shift=0, mask=4294967295, attrs=...)
    at ../system/memory.c:497
13 0x0000560640f270a6 in access_with_adjusted_size

     (addr=12, value=0x7fc86b7bc628, size=4, access_size_min=1, access_size_max=4, access_fn=0x560640f26c8d <memory_region_write_accessor>, mr=0x560643c66540, attrs=...) at ../system/memory.c:573
14 0x0000560640f2a2b5 in memory_region_dispatch_write (mr=0x560643c66540, addr=12, data=0, op=MO_32, attrs=...)
    at ../system/memory.c:1521
15 0x0000560640f37bac in flatview_write_continue
    (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., ptr=0x7fc871e9c028, len=4, addr1=12, l=4, mr=0x560643c66540)
    at ../system/physmem.c:2714
16 0x0000560640f37d0f in flatview_write
    (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4) at ../system/physmem.c:2756
17 0x0000560640f380bf in address_space_write
    (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4)
    at ../system/physmem.c:2863
18 0x0000560640f3812c in address_space_rw
    (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4, is_write=true) at ../system/physmem.c:2873
--Type <RET> for more, q to quit, c to continue without paging--
19 0x0000560640f8aa55 in kvm_cpu_exec (cpu=0x560642f205e0) at ../accel/kvm/kvm-all.c:2915
20 0x0000560640f8d731 in kvm_vcpu_thread_fn (arg=0x560642f205e0) at ../accel/kvm/kvm-accel-ops.c:51
21 0x00005606411949f4 in qemu_thread_start (args=0x560642f292b0) at ../util/qemu-thread-posix.c:541
22 0x00007fc87148cdcd in start_thread (arg=<optimized out>) at pthread_create.c:442
23 0x00007fc871512630 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
(gdb)
Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 hw/virtio/virtio-pci.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 1a7039fb0c..b3b1a4a66f 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1570,7 +1570,22 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
+        vector = vdev->config_vector;
         vdev->config_vector = val;
+        /*
+         * If the value was changed after DRIVER_OK was set, it means that
+         * we need to release the old vector and set up the new vector.
+         */
+        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            /*check if use the irqfd*/
+            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
+            if (val != VIRTIO_NO_VECTOR) {
+                kvm_virtio_pci_vector_use_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
+            }
+            if (vector != VIRTIO_NO_VECTOR) {
+                kvm_virtio_pci_vector_release_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
+            }
+        }
         break;
     case VIRTIO_PCI_COMMON_STATUS:
         if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
@@ -1611,6 +1626,21 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
             val = VIRTIO_NO_VECTOR;
         }
         virtio_queue_set_vector(vdev, vdev->queue_sel, val);
+
+        /*
+         * If the value was changed after DRIVER_OK was set, it means that
+         * we need to release the old vector and set up the new vector.
+         */
+        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            /*check if use the irqfd*/
+            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
+            if (val != VIRTIO_NO_VECTOR) {
+                kvm_virtio_pci_vector_use_one(proxy, vdev->queue_sel);
+            }
+            if (vector != VIRTIO_NO_VECTOR) {
+                kvm_virtio_pci_vector_release_one(proxy, vdev->queue_sel);
+            }
+        }
         break;
     case VIRTIO_PCI_COMMON_Q_ENABLE:
         if (val == 1) {
-- 
2.43.0

On Thu, Apr 11, 2024 at 12:12:00AM +0800, Cindy Lu wrote:
> During the booting process of the non-standard image, the behavior of the
> called function in qemu is as follows:
> 
> 1. vhost_net_stop() was triggered by guest image. This will call the function
> virtio_pci_set_guest_notifiers() with assgin= false,
> virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0
> 
> 2. virtio_reset() was triggered, this will set configure vector to VIRTIO_NO_VECTOR
> 
> 3.vhost_net_start() was called (at this time, the configure vector is
> still VIRTIO_NO_VECTOR) and then call virtio_pci_set_guest_notifiers() with
> assgin=true, so the irqfd for vector 0 is still not "init" during this process
> 
> 4. The system continues to boot and sets the vector back to 0. After that
> msix_fire_vector_notifier() was triggered to unmask the vector 0 and  meet the crash
> 
> To fix the issue, we need to support changing the vector after VIRTIO_CONFIG_S_DRIVER_OK is set.
> 
> (gdb) bt
> 0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0)
>     at pthread_kill.c:44
> 1  0x00007fc87148ec53 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
> 2  0x00007fc87143e956 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
> 3  0x00007fc8714287f4 in __GI_abort () at abort.c:79
> 4  0x00007fc87142871b in __assert_fail_base
>     (fmt=0x7fc8715bbde0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=<optimized out>) at assert.c:92
> 5  0x00007fc871437536 in __GI___assert_fail
>     (assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=0x5606413f06f0 <__PRETTY_FUNCTION__.19> "kvm_irqchip_commit_routes") at assert.c:101
> 6  0x0000560640f884b5 in kvm_irqchip_commit_routes (s=0x560642cae1f0) at ../accel/kvm/kvm-all.c:1837
> 7  0x0000560640c98f8e in virtio_pci_one_vector_unmask
>     (proxy=0x560643c65f00, queue_no=4294967295, vector=0, msg=..., n=0x560643c6e4c8)
>     at ../hw/virtio/virtio-pci.c:1005
> 8  0x0000560640c99201 in virtio_pci_vector_unmask (dev=0x560643c65f00, vector=0, msg=...)
>     at ../hw/virtio/virtio-pci.c:1070
> 9  0x0000560640bc402e in msix_fire_vector_notifier (dev=0x560643c65f00, vector=0, is_masked=false)
>     at ../hw/pci/msix.c:120
> 10 0x0000560640bc40f1 in msix_handle_mask_update (dev=0x560643c65f00, vector=0, was_masked=true)
>     at ../hw/pci/msix.c:140
> 11 0x0000560640bc4503 in msix_table_mmio_write (opaque=0x560643c65f00, addr=12, val=0, size=4)
>     at ../hw/pci/msix.c:231
> 12 0x0000560640f26d83 in memory_region_write_accessor
>     (mr=0x560643c66540, addr=12, value=0x7fc86b7bc628, size=4, shift=0, mask=4294967295, attrs=...)
>     at ../system/memory.c:497
> 13 0x0000560640f270a6 in access_with_adjusted_size
> 
>      (addr=12, value=0x7fc86b7bc628, size=4, access_size_min=1, access_size_max=4, access_fn=0x560640f26c8d <memory_region_write_accessor>, mr=0x560643c66540, attrs=...) at ../system/memory.c:573
> 14 0x0000560640f2a2b5 in memory_region_dispatch_write (mr=0x560643c66540, addr=12, data=0, op=MO_32, attrs=...)
>     at ../system/memory.c:1521
> 15 0x0000560640f37bac in flatview_write_continue
>     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., ptr=0x7fc871e9c028, len=4, addr1=12, l=4, mr=0x560643c66540)
>     at ../system/physmem.c:2714
> 16 0x0000560640f37d0f in flatview_write
>     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4) at ../system/physmem.c:2756
> 17 0x0000560640f380bf in address_space_write
>     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4)
>     at ../system/physmem.c:2863
> 18 0x0000560640f3812c in address_space_rw
>     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4, is_write=true) at ../system/physmem.c:2873
> --Type <RET> for more, q to quit, c to continue without paging--
> 19 0x0000560640f8aa55 in kvm_cpu_exec (cpu=0x560642f205e0) at ../accel/kvm/kvm-all.c:2915
> 20 0x0000560640f8d731 in kvm_vcpu_thread_fn (arg=0x560642f205e0) at ../accel/kvm/kvm-accel-ops.c:51
> 21 0x00005606411949f4 in qemu_thread_start (args=0x560642f292b0) at ../util/qemu-thread-posix.c:541
> 22 0x00007fc87148cdcd in start_thread (arg=<optimized out>) at pthread_create.c:442
> 23 0x00007fc871512630 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
> (gdb)
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>  hw/virtio/virtio-pci.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 1a7039fb0c..b3b1a4a66f 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1570,7 +1570,22 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
>          } else {
>              val = VIRTIO_NO_VECTOR;
>          }
> +        vector = vdev->config_vector;
>          vdev->config_vector = val;
> +        /*
> +         * If the value was changed after DRIVER_OK was set, it means that
> +         * we need to release the old vector and set up the new vector.
> +         */
> +        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +            /*check if use the irqfd*/
> +            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> +            if (val != VIRTIO_NO_VECTOR) {
> +                kvm_virtio_pci_vector_use_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
> +            }
> +            if (vector != VIRTIO_NO_VECTOR) {
> +                kvm_virtio_pci_vector_release_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
> +            }
> +        }
>          break;
>      case VIRTIO_PCI_COMMON_STATUS:
>          if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> @@ -1611,6 +1626,21 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
>              val = VIRTIO_NO_VECTOR;
>          }
>          virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> +
> +        /*
> +         * If the value was changed after DRIVER_OK was set, it means that
> +         * we need to release the old vector and set up the new vector.
> +         */
> +        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +            /*check if use the irqfd*/

by comment style

> +            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> +            if (val != VIRTIO_NO_VECTOR) {
> +                kvm_virtio_pci_vector_use_one(proxy, vdev->queue_sel);
> +            }
> +            if (vector != VIRTIO_NO_VECTOR) {
> +                kvm_virtio_pci_vector_release_one(proxy, vdev->queue_sel);
> +            }

does it matter in which order to do this?
if we release 1st there's more of a chance use will succeeed.

I would also check val != vector
if value did not change there is nothing to do.

> +        }
>          break;
>      case VIRTIO_PCI_COMMON_Q_ENABLE:
>          if (val == 1) {
> -- 
> 2.43.0

On Thu, Apr 11, 2024 at 12:18 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, Apr 11, 2024 at 12:12:00AM +0800, Cindy Lu wrote:
> > During the booting process of the non-standard image, the behavior of the
> > called function in qemu is as follows:
> >
> > 1. vhost_net_stop() was triggered by guest image. This will call the function
> > virtio_pci_set_guest_notifiers() with assgin= false,
> > virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0
> >
> > 2. virtio_reset() was triggered, this will set configure vector to VIRTIO_NO_VECTOR
> >
> > 3.vhost_net_start() was called (at this time, the configure vector is
> > still VIRTIO_NO_VECTOR) and then call virtio_pci_set_guest_notifiers() with
> > assgin=true, so the irqfd for vector 0 is still not "init" during this process
> >
> > 4. The system continues to boot and sets the vector back to 0. After that
> > msix_fire_vector_notifier() was triggered to unmask the vector 0 and  meet the crash
> >
> > To fix the issue, we need to support changing the vector after VIRTIO_CONFIG_S_DRIVER_OK is set.
> >
> > (gdb) bt
> > 0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0)
> >     at pthread_kill.c:44
> > 1  0x00007fc87148ec53 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
> > 2  0x00007fc87143e956 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
> > 3  0x00007fc8714287f4 in __GI_abort () at abort.c:79
> > 4  0x00007fc87142871b in __assert_fail_base
> >     (fmt=0x7fc8715bbde0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=<optimized out>) at assert.c:92
> > 5  0x00007fc871437536 in __GI___assert_fail
> >     (assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=0x5606413f06f0 <__PRETTY_FUNCTION__.19> "kvm_irqchip_commit_routes") at assert.c:101
> > 6  0x0000560640f884b5 in kvm_irqchip_commit_routes (s=0x560642cae1f0) at ../accel/kvm/kvm-all.c:1837
> > 7  0x0000560640c98f8e in virtio_pci_one_vector_unmask
> >     (proxy=0x560643c65f00, queue_no=4294967295, vector=0, msg=..., n=0x560643c6e4c8)
> >     at ../hw/virtio/virtio-pci.c:1005
> > 8  0x0000560640c99201 in virtio_pci_vector_unmask (dev=0x560643c65f00, vector=0, msg=...)
> >     at ../hw/virtio/virtio-pci.c:1070
> > 9  0x0000560640bc402e in msix_fire_vector_notifier (dev=0x560643c65f00, vector=0, is_masked=false)
> >     at ../hw/pci/msix.c:120
> > 10 0x0000560640bc40f1 in msix_handle_mask_update (dev=0x560643c65f00, vector=0, was_masked=true)
> >     at ../hw/pci/msix.c:140
> > 11 0x0000560640bc4503 in msix_table_mmio_write (opaque=0x560643c65f00, addr=12, val=0, size=4)
> >     at ../hw/pci/msix.c:231
> > 12 0x0000560640f26d83 in memory_region_write_accessor
> >     (mr=0x560643c66540, addr=12, value=0x7fc86b7bc628, size=4, shift=0, mask=4294967295, attrs=...)
> >     at ../system/memory.c:497
> > 13 0x0000560640f270a6 in access_with_adjusted_size
> >
> >      (addr=12, value=0x7fc86b7bc628, size=4, access_size_min=1, access_size_max=4, access_fn=0x560640f26c8d <memory_region_write_accessor>, mr=0x560643c66540, attrs=...) at ../system/memory.c:573
> > 14 0x0000560640f2a2b5 in memory_region_dispatch_write (mr=0x560643c66540, addr=12, data=0, op=MO_32, attrs=...)
> >     at ../system/memory.c:1521
> > 15 0x0000560640f37bac in flatview_write_continue
> >     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., ptr=0x7fc871e9c028, len=4, addr1=12, l=4, mr=0x560643c66540)
> >     at ../system/physmem.c:2714
> > 16 0x0000560640f37d0f in flatview_write
> >     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4) at ../system/physmem.c:2756
> > 17 0x0000560640f380bf in address_space_write
> >     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4)
> >     at ../system/physmem.c:2863
> > 18 0x0000560640f3812c in address_space_rw
> >     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4, is_write=true) at ../system/physmem.c:2873
> > --Type <RET> for more, q to quit, c to continue without paging--
> > 19 0x0000560640f8aa55 in kvm_cpu_exec (cpu=0x560642f205e0) at ../accel/kvm/kvm-all.c:2915
> > 20 0x0000560640f8d731 in kvm_vcpu_thread_fn (arg=0x560642f205e0) at ../accel/kvm/kvm-accel-ops.c:51
> > 21 0x00005606411949f4 in qemu_thread_start (args=0x560642f292b0) at ../util/qemu-thread-posix.c:541
> > 22 0x00007fc87148cdcd in start_thread (arg=<optimized out>) at pthread_create.c:442
> > 23 0x00007fc871512630 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
> > (gdb)
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> >  hw/virtio/virtio-pci.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 1a7039fb0c..b3b1a4a66f 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1570,7 +1570,22 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >          } else {
> >              val = VIRTIO_NO_VECTOR;
> >          }
> > +        vector = vdev->config_vector;
> >          vdev->config_vector = val;
> > +        /*
> > +         * If the value was changed after DRIVER_OK was set, it means that
> > +         * we need to release the old vector and set up the new vector.
> > +         */
> > +        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > +            /*check if use the irqfd*/
> > +            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> > +            if (val != VIRTIO_NO_VECTOR) {
> > +                kvm_virtio_pci_vector_use_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
> > +            }
> > +            if (vector != VIRTIO_NO_VECTOR) {
> > +                kvm_virtio_pci_vector_release_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
> > +            }
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_STATUS:
> >          if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > @@ -1611,6 +1626,21 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >              val = VIRTIO_NO_VECTOR;
> >          }
> >          virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> > +
> > +        /*
> > +         * If the value was changed after DRIVER_OK was set, it means that
> > +         * we need to release the old vector and set up the new vector.
> > +         */
> > +        if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > +            /*check if use the irqfd*/
>
> by comment style
will fix this
>
> > +            (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> > +            if (val != VIRTIO_NO_VECTOR) {
> > +                kvm_virtio_pci_vector_use_one(proxy, vdev->queue_sel);
> > +            }
> > +            if (vector != VIRTIO_NO_VECTOR) {
> > +                kvm_virtio_pci_vector_release_one(proxy, vdev->queue_sel);
> > +            }
>
> does it matter in which order to do this?
> if we release 1st there's more of a chance use will succeeed.
>
> I would also check val != vector
> if value did not change there is nothing to do.
>
Sure, thanks Michael, will send a new version soon
thanks
cindy
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_Q_ENABLE:
> >          if (val == 1) {
> > --
> > 2.43.0
>