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Re: [Qemu-devel] [RFC v2 3/9] virtio: stop virtqueue processing if devic


From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [RFC v2 3/9] virtio: stop virtqueue processing if device is broken
Date: Wed, 30 Mar 2016 13:21:53 +0100
User-agent: Mutt/1.5.24 (2015-08-30)

On Tue, Mar 29, 2016 at 06:58:03PM +0200, Cornelia Huck wrote:
> On Tue, 29 Mar 2016 17:12:55 +0100
> Stefan Hajnoczi <address@hidden> wrote:
> 
> > QEMU prints an error message and exits when the device enters an invalid
> > state.  Terminating the process is heavy-handed.  The guest may still be
> > able to function even if there is a bug in a virtio guest driver.
> > 
> > Moreover, exiting is a bug in nested virtualization where a nested guest
> > could DoS other nested guests by killing a pass-through virtio device.
> > I don't think this configuration is possible today but it is likely in
> > the future.
> > 
> > If the broken flag is set, do not process virtqueues or write back used
> > descriptors.  The broken flag can be cleared again by resetting the
> > device.
> > 
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> >  hw/virtio/virtio.c         | 39 +++++++++++++++++++++++++++++++++++++++
> >  include/hw/virtio/virtio.h |  3 +++
> >  2 files changed, 42 insertions(+)
> 
> > +void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, 
> > ...)
> > +{
> > +    va_list ap;
> > +
> > +    va_start(ap, fmt);
> > +    error_vreport(fmt, ap);
> > +    va_end(ap);
> > +
> > +    vdev->broken = true;
> > +
> > +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> > +        vdev->status |= VIRTIO_CONFIG_S_NEEDS_RESET;
> 
> virtio_set_status()?

Will fix in next revision

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