Re: [PATCH v2 2/5] virtio-net: align ctrl_vq index for non-mq guest for vhost_vdpa

[Jason Wang]

On Sat, Apr 30, 2022 at 9:13 AM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>
>
>
> On 4/28/2022 7:23 PM, Jason Wang wrote:
> >
> > 在 2022/4/27 16:30, Si-Wei Liu 写道:
> >> With MQ enabled vdpa device and non-MQ supporting guest e.g.
> >> booting vdpa with mq=on over OVMF of single vqp, below assert
> >> failure is seen:
> >>
> >> ../hw/virtio/vhost-vdpa.c:560: vhost_vdpa_get_vq_index: Assertion
> >> `idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs' failed.
> >>
> >> 0  0x00007f8ce3ff3387 in raise () at /lib64/libc.so.6
> >> 1  0x00007f8ce3ff4a78 in abort () at /lib64/libc.so.6
> >> 2  0x00007f8ce3fec1a6 in __assert_fail_base () at /lib64/libc.so.6
> >> 3  0x00007f8ce3fec252 in  () at /lib64/libc.so.6
> >> 4  0x0000558f52d79421 in vhost_vdpa_get_vq_index (dev=<optimized
> >> out>, idx=<optimized out>) at ../hw/virtio/vhost-vdpa.c:563
> >> 5  0x0000558f52d79421 in vhost_vdpa_get_vq_index (dev=<optimized
> >> out>, idx=<optimized out>) at ../hw/virtio/vhost-vdpa.c:558
> >> 6  0x0000558f52d7329a in vhost_virtqueue_mask (hdev=0x558f55c01800,
> >> vdev=0x558f568f91f0, n=2, mask=<optimized out>) at
> >> ../hw/virtio/vhost.c:1557
> >> 7  0x0000558f52c6b89a in virtio_pci_set_guest_notifier
> >> (d=d@entry=0x558f568f0f60, n=n@entry=2, assign=assign@entry=true,
> >> with_irqfd=with_irqfd@entry=false)
> >>     at ../hw/virtio/virtio-pci.c:974
> >> 8  0x0000558f52c6c0d8 in virtio_pci_set_guest_notifiers
> >> (d=0x558f568f0f60, nvqs=3, assign=true) at
> >> ../hw/virtio/virtio-pci.c:1019
> >> 9  0x0000558f52bf091d in vhost_net_start
> >> (dev=dev@entry=0x558f568f91f0, ncs=0x558f56937cd0,
> >> data_queue_pairs=data_queue_pairs@entry=1, cvq=cvq@entry=1)
> >>     at ../hw/net/vhost_net.c:361
> >> 10 0x0000558f52d4e5e7 in virtio_net_set_status (status=<optimized
> >> out>, n=0x558f568f91f0) at ../hw/net/virtio-net.c:289
> >> 11 0x0000558f52d4e5e7 in virtio_net_set_status (vdev=0x558f568f91f0,
> >> status=15 '\017') at ../hw/net/virtio-net.c:370
> >> 12 0x0000558f52d6c4b2 in virtio_set_status
> >> (vdev=vdev@entry=0x558f568f91f0, val=val@entry=15 '\017') at
> >> ../hw/virtio/virtio.c:1945
> >> 13 0x0000558f52c69eff in virtio_pci_common_write
> >> (opaque=0x558f568f0f60, addr=<optimized out>, val=<optimized out>,
> >> size=<optimized out>) at ../hw/virtio/virtio-pci.c:1292
> >> 14 0x0000558f52d15d6e in memory_region_write_accessor
> >> (mr=0x558f568f19d0, addr=20, value=<optimized out>, size=1,
> >> shift=<optimized out>, mask=<optimized out>, attrs=...)
> >>     at ../softmmu/memory.c:492
> >> 15 0x0000558f52d127de in access_with_adjusted_size
> >> (addr=addr@entry=20, value=value@entry=0x7f8cdbffe748,
> >> size=size@entry=1, access_size_min=<optimized out>,
> >> access_size_max=<optimized out>, access_fn=0x558f52d15cf0
> >> <memory_region_write_accessor>, mr=0x558f568f19d0, attrs=...) at
> >> ../softmmu/memory.c:554
> >> 16 0x0000558f52d157ef in memory_region_dispatch_write
> >> (mr=mr@entry=0x558f568f19d0, addr=20, data=<optimized out>,
> >> op=<optimized out>, attrs=attrs@entry=...)
> >>     at ../softmmu/memory.c:1504
> >> 17 0x0000558f52d078e7 in flatview_write_continue
> >> (fv=fv@entry=0x7f8accbc3b90, addr=addr@entry=103079215124, attrs=...,
> >> ptr=ptr@entry=0x7f8ce6300028, len=len@entry=1, addr1=<optimized out>,
> >> l=<optimized out>, mr=0x558f568f19d0) at
> >> /home/opc/qemu-upstream/include/qemu/host-utils.h:165
> >> 18 0x0000558f52d07b06 in flatview_write (fv=0x7f8accbc3b90,
> >> addr=103079215124, attrs=..., buf=0x7f8ce6300028, len=1) at
> >> ../softmmu/physmem.c:2822
> >> 19 0x0000558f52d0b36b in address_space_write (as=<optimized out>,
> >> addr=<optimized out>, attrs=..., buf=buf@entry=0x7f8ce6300028,
> >> len=<optimized out>)
> >>     at ../softmmu/physmem.c:2914
> >> 20 0x0000558f52d0b3da in address_space_rw (as=<optimized out>,
> >> addr=<optimized out>, attrs=...,
> >>     attrs@entry=..., buf=buf@entry=0x7f8ce6300028, len=<optimized
> >> out>, is_write=<optimized out>) at ../softmmu/physmem.c:2924
> >> 21 0x0000558f52dced09 in kvm_cpu_exec (cpu=cpu@entry=0x558f55c2da60)
> >> at ../accel/kvm/kvm-all.c:2903
> >> 22 0x0000558f52dcfabd in kvm_vcpu_thread_fn
> >> (arg=arg@entry=0x558f55c2da60) at ../accel/kvm/kvm-accel-ops.c:49
> >> 23 0x0000558f52f9f04a in qemu_thread_start (args=<optimized out>) at
> >> ../util/qemu-thread-posix.c:556
> >> 24 0x00007f8ce4392ea5 in start_thread () at /lib64/libpthread.so.0
> >> 25 0x00007f8ce40bb9fd in clone () at /lib64/libc.so.6
> >>
> >> The cause for the assert failure is due to that the vhost_dev index
> >> for the ctrl vq was not aligned with actual one in use by the guest.
> >> Upon multiqueue feature negotiation in virtio_net_set_multiqueue(),
> >> if guest doesn't support multiqueue, the guest vq layout would shrink
> >> to a single queue pair, consisting of 3 vqs in total (rx, tx and ctrl).
> >> This results in ctrl_vq taking a different vhost_dev group index than
> >> the default. We can map vq to the correct vhost_dev group by checking
> >> if MQ is supported by guest and successfully negotiated. Since the
> >> MQ feature is only present along with CTRL_VQ, we make sure the index
> >> 2 is only meant for the control vq while MQ is not supported by guest.
> >>
> >> Fixes: 22288fe ("virtio-net: vhost control virtqueue support")
> >> Suggested-by: Jason Wang <jasowang@redhat.com>
> >> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> >> ---
> >>   hw/net/virtio-net.c | 22 ++++++++++++++++++++--
> >>   1 file changed, 20 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >> index ffb3475..8ca0b80 100644
> >> --- a/hw/net/virtio-net.c
> >> +++ b/hw/net/virtio-net.c
> >> @@ -3171,8 +3171,17 @@ static NetClientInfo net_virtio_info = {
> >>   static bool virtio_net_guest_notifier_pending(VirtIODevice *vdev,
> >> int idx)
> >>   {
> >>       VirtIONet *n = VIRTIO_NET(vdev);
> >> -    NetClientState *nc = qemu_get_subqueue(n->nic, vq2q(idx));
> >> +    NetClientState *nc;
> >>       assert(n->vhost_started);
> >> +    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_MQ) && idx == 2) {
> >> +        if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> >> +           error_report("virtio-net: bogus vq index ignored");
> >
> >
> > This seems trigger-able by guest.
> Yes, this is trigger-able by either buggy guest or buggy migration flow
> (could be due to remote buggy QEMU). I was not sure if it'll be too
> determined to use LOG_GUEST_ERROR, and doesn't seem it's the convention
> to log guest error in the same file. What's your preference here, switch
> to LOG_GUEST_ERROR, or simply drop the error message?

I think it's better to use LOG_GUEST_ERROR here.

Thanks

>
> Thanks,
> -Siwei
>
> >
> > Other looks good.
> >
> > Thanks
> >
> >
> >> +           return false;
> >> +        }
> >> +        nc = qemu_get_subqueue(n->nic, n->max_queue_pairs);
> >> +    } else {
> >> +        nc = qemu_get_subqueue(n->nic, vq2q(idx));
> >> +    }
> >>       return vhost_net_virtqueue_pending(get_vhost_net(nc->peer), idx);
> >>   }
> >>   @@ -3180,8 +3189,17 @@ static void
> >> virtio_net_guest_notifier_mask(VirtIODevice *vdev, int idx,
> >>                                              bool mask)
> >>   {
> >>       VirtIONet *n = VIRTIO_NET(vdev);
> >> -    NetClientState *nc = qemu_get_subqueue(n->nic, vq2q(idx));
> >> +    NetClientState *nc;
> >>       assert(n->vhost_started);
> >> +    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_MQ) && idx == 2) {
> >> +        if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> >> +           error_report("virtio-net: bogus vq index ignored");
> >> +           return;
> >> +        }
> >> +        nc = qemu_get_subqueue(n->nic, n->max_queue_pairs);
> >> +    } else {
> >> +        nc = qemu_get_subqueue(n->nic, vq2q(idx));
> >> +    }
> >>       vhost_net_virtqueue_mask(get_vhost_net(nc->peer),
> >>                                vdev, idx, mask);
> >>   }
> >
>