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

[Si-Wei Liu <si-wei.liu@oracle.com>]

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?

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);
>>   }
>