Re: [PATCH v3 2/6] virtio-net: align ctrl_vq index for non-mq guest for vhost_vdpa

[Jason Wang]

On Fri, May 6, 2022 at 12:54 PM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>
> 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 ensure 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>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  hw/net/virtio-net.c | 33 +++++++++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index ffb3475..f0bb29c 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -14,6 +14,7 @@
>  #include "qemu/osdep.h"
>  #include "qemu/atomic.h"
>  #include "qemu/iov.h"
> +#include "qemu/log.h"
>  #include "qemu/main-loop.h"
>  #include "qemu/module.h"
>  #include "hw/virtio/virtio.h"
> @@ -3171,8 +3172,22 @@ 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) {
> +        /* Must guard against invalid features and bogus queue index
> +         * from being set by malicious guest, or penetrated through
> +         * buggy migration stream.
> +         */
> +        if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "%s: bogus vq index ignored\n", __func__);
> +            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 +3195,22 @@ 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) {
> +        /* Must guard against invalid features and bogus queue index
> +         * from being set by malicious guest, or penetrated through
> +         * buggy migration stream.
> +         */
> +        if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "%s: bogus vq index ignored\n", __func__);
> +            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);
>  }
> --
> 1.8.3.1
>