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 <l...@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
