Re: [SeaBIOS] [PATCH] init_virtio_scsi(): reset the HBA before freeing its virtio ring

[Kevin O'Connor]

On Wed, Jan 15, 2014 at 11:01:59AM +0100, Paolo Bonzini wrote:
> Il 15/01/2014 02:48, Laszlo Ersek ha scritto:
> > When init_virtio_scsi() finds no SCSI targets connected to the HBA, it
> > frees the virtio ring. Other code in SeaBIOS proceeds to overwrite the
> > area. However, the ring is in use by qemu at that point -- not only did we
> > report the (ACK|DRIVER|DRIVER_OK) status earlier, we even communicated
> > over the ring.
> >
> > Of course SeaBIOS doesn't "kick" the HBA ever again, hence qemu has no
> > reason to look at the ring. However, when qemu uses KVM acceleration, and
> > ioeventfd is enabled for the HBA, then a vmstate change to "running"
> > (including stop->cont monitor commands and incoming migration) "forces" a
> > kick (see qemu commit 25db9ebe). Qemu then tries to interpret whatever
> > unrelated guest data is in the HBA's original ring area, as virtio
> > protocol. Qemu exits upon seeing the garbage.
> >
> > init_virtio_scsi() should reset the HBA before allowing the virtio ring
> > memory to be reused. Device reset causes the hypervisor to drop its
> > references.
> >
> > This change is justified / underpinned by pure virtio-spec compliance as
> > well.
> >
> > Related RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1013418
> >
> > Signed-off-by: Laszlo Ersek

[...]
> Thanks Laszlo!
>
> Reviewed-by: Paolo Bonzini
>
> Paolo

Thanks Laszlo - I'm sure that wasn't easy to find.  I've pushed the
patch.

-Kevin