On Sat, Apr 2, 2022 at 6:32 AM Si-Wei Liu <si-wei....@oracle.com> wrote:
>
>
>
> On 3/31/2022 1:39 AM, Jason Wang wrote:
> > On Wed, Mar 30, 2022 at 11:48 PM Si-Wei Liu <si-wei....@oracle.com> wrote:
> >>
> >>
> >> On 3/30/2022 2:00 AM, Jason Wang wrote:
> >>> On Wed, Mar 30, 2022 at 2:33 PM Si-Wei Liu <si-wei....@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 make sure the index
> >>>> 2 is only meant for the control vq while MQ is not supported by guest.
> >>>>
> >>>> Be noted if QEMU or guest doesn't support control vq, there's no bother
> >>>> exposing vhost_dev and guest notifier for the control vq. Since
> >>>> vhost_net_start/stop implies DRIVER_OK is set in device status, feature
> >>>> negotiation should be completed when reaching virtio_net_vhost_status().
> >>>>
> >>>> Fixes: 22288fe ("virtio-net: vhost control virtqueue support")
> >>>> Suggested-by: Jason Wang <jasow...@redhat.com>
> >>>> Signed-off-by: Si-Wei Liu <si-wei....@oracle.com>
> >>>> ---
> >>>> hw/net/virtio-net.c | 19 ++++++++++++++++---
> >>>> 1 file changed, 16 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >>>> index 1067e72..484b215 100644
> >>>> --- a/hw/net/virtio-net.c
> >>>> +++ b/hw/net/virtio-net.c
> >>>> @@ -245,7 +245,8 @@ static void virtio_net_vhost_status(VirtIONet *n,
> >>>> uint8_t status)
> >>>> VirtIODevice *vdev = VIRTIO_DEVICE(n);
> >>>> NetClientState *nc = qemu_get_queue(n->nic);
> >>>> int queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
> >>>> - int cvq = n->max_ncs - n->max_queue_pairs;
> >>>> + int cvq = virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) ?
> >>>> + n->max_ncs - n->max_queue_pairs : 0;
> >>> Let's use a separate patch for this.
> >> Yes, I can do that. Then the new patch will become a requisite for this
> >> patch.
> >>
> >>>> if (!get_vhost_net(nc->peer)) {
> >>>> return;
> >>>> @@ -3170,8 +3171,14 @@ 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) {
> >>>> + assert(virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ));
> >>> This assert seems guest trigger-able. If yes, I would remove this or
> >>> replace it with log_guest_error.
> >> This assert actually is relevant to the cvq change in
> >> virtio_net_vhost_status(). Since the same check on VIRTIO_NET_F_CTRL_VQ
> >> has been done earlier, it is assured that CTRL_VQ is negotiated when
> >> getting here.
> >> Noted the vhost_started is asserted in the same function, which in turn
> >> implies DRIVER_OK is set meaning feature negotiation is complete. I
> >> can't easily think of a scenario which guest may inadvertently or
> >> purposely trigger the assert?
> > So the code can be triggered like e.g unmasking:
> >
> > virtio_pci_vq_vector_unmask()
> > k->guest_notifier_pending()
> Hmmm, are you concerned more about idx being invalid, or
> VIRTIO_NET_F_CTRL_VQ getting cleared?
Something like this, we can't let a buggy driver crash into Qemu.
>
> virtio_pci_vector_unmask() has validation through virtio_queue_get_num()
> that ensures the vq index is valid.
Actually not, it just check whether the vq size is set:
int virtio_queue_get_num(VirtIODevice *vdev, int n)
{
return vdev->vq[n].vring.num;
}
> While it doesn't seem possible for
> VIRTIO_NET_F_CTRL_VQ to be cleared without device reset first,
Probably, since we had a check in virtio_set_features():
/*
* The driver must not attempt to set features after feature negotiation
* has finished.
*/
if (vdev->status & VIRTIO_CONFIG_S_FEATURES_OK) {
return -EINVAL;
}
But another interesting part is that the guest_feautres come from the
migration stream as well:
static const VMStateDescription vmstate_virtio_64bit_features = {
.name = "virtio/64bit_features",
.version_id = 1,
.minimum_version_id = 1,
.needed = &virtio_64bit_features_needed,
.fields = (VMStateField[]) {
VMSTATE_UINT64(guest_features, VirtIODevice),
VMSTATE_END_OF_LIST()
}
};
We should also be ready to let the buggy migration flow to crash us.
>during
> which the pending event left over on guest notifier eventfd should have
> been completed within virtio_pci_set_guest_notifiers(false) before
> vhost_net_stop() returns. If I am not missing something here, I guess
> we're probably fine?
I'm not sure I got here, but the mask/unmask is not necessarily
related to vhost stop. E.g it can happen if guest want to change IRQ
affinity.
Thanks
>
> -Siwei
>
> >
> > Thanks
> >
> >
> >> -Siwei
> >>
> >>>> + 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);
> >>>> }
> >>>>
> >>>> @@ -3179,8 +3186,14 @@ 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) {
> >>>> + assert(virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ));
> >>> And this.
> >>>
> >>> Thanks
> >>>
> >>>
> >>>> + 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
> >>>>
>
