Re: [PATCH] virtio-pci: fix virtio_pci_queue_enabled()

[Michael S. Tsirkin]

On Tue, Jul 28, 2020 at 11:55:16AM +0800, Jason Wang wrote:
> 
> On 2020/7/27 下午11:33, Laurent Vivier wrote:
> > In legacy mode, virtio_pci_queue_enabled() falls back to
> > virtio_queue_enabled() to know if the queue is enabled.
> > 
> > But virtio_queue_enabled() calls again virtio_pci_queue_enabled()
> > if k->queue_enabled is set. This ends in a crash after a stack
> > overflow.
> > 
> > The problem can be reproduced with
> > "-device virtio-net-pci,disable-legacy=off,disable-modern=true
> >   -net tap,vhost=on"
> > 
> > And a look to the backtrace is very explicit:
> > 
> >      ...
> >      #4  0x000000010029a438 in virtio_queue_enabled ()
> >      #5  0x0000000100497a9c in virtio_pci_queue_enabled ()
> >      ...
> >      #130902 0x000000010029a460 in virtio_queue_enabled ()
> >      #130903 0x0000000100497a9c in virtio_pci_queue_enabled ()
> >      #130904 0x000000010029a460 in virtio_queue_enabled ()
> >      #130905 0x0000000100454a20 in vhost_net_start ()
> >      ...
> > 
> > This patch fixes the problem by introducing a new function
> > for the legacy case and calls it from virtio_pci_queue_enabled().
> > It also calls it from virtio_queue_enabled() to avoid code duplication.
> > 
> > Fixes: f19bcdfedd53 ("virtio-pci: implement queue_enabled method")
> > Cc: Jason Wang <jasowang@redhat.com>
> > Cc: Cindy Lu <lulu@redhat.com>
> > CC: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> 
> 
> Queued for rc2.
> 
> Thanks

Oh I didn't realise you are merging virtio patches.
If you do, pls include this tag:

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>


> 
> > ---
> >   hw/virtio/virtio-pci.c     | 2 +-
> >   hw/virtio/virtio.c         | 7 ++++++-
> >   include/hw/virtio/virtio.h | 1 +
> >   3 files changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index ada1101d07bf..4ad3ad81a2cf 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1116,7 +1116,7 @@ static bool virtio_pci_queue_enabled(DeviceState *d, 
> > int n)
> >           return proxy->vqs[vdev->queue_sel].enabled;
> >       }
> > -    return virtio_queue_enabled(vdev, n);
> > +    return virtio_queue_enabled_legacy(vdev, n);
> >   }
> >   static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index 546a198e79b0..e98302521769 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -3309,6 +3309,11 @@ hwaddr virtio_queue_get_desc_addr(VirtIODevice 
> > *vdev, int n)
> >       return vdev->vq[n].vring.desc;
> >   }
> > +bool virtio_queue_enabled_legacy(VirtIODevice *vdev, int n)
> > +{
> > +    return virtio_queue_get_desc_addr(vdev, n) != 0;
> > +}
> > +
> >   bool virtio_queue_enabled(VirtIODevice *vdev, int n)
> >   {
> >       BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> > @@ -3317,7 +3322,7 @@ bool virtio_queue_enabled(VirtIODevice *vdev, int n)
> >       if (k->queue_enabled) {
> >           return k->queue_enabled(qbus->parent, n);
> >       }
> > -    return virtio_queue_get_desc_addr(vdev, n) != 0;
> > +    return virtio_queue_enabled_legacy(vdev, n);
> >   }
> >   hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n)
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index 198ffc762678..e424df12cf6d 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -295,6 +295,7 @@ typedef struct VirtIORNGConf VirtIORNGConf;
> >                         VIRTIO_F_RING_PACKED, false)
> >   hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n);
> > +bool virtio_queue_enabled_legacy(VirtIODevice *vdev, int n);
> >   bool virtio_queue_enabled(VirtIODevice *vdev, int n);
> >   hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n);
> >   hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);