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

[Laszlo Ersek]

On 01/17/14 18:17, Kevin O'Connor wrote:
> 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 <lersek at redhat.com>
> [...]
>> Thanks Laszlo!
>>
>> Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
>>
>> Paolo
> 
> Thanks Laszlo - I'm sure that wasn't easy to find.

No, it wasn't; the BZ is public and anyone can see my struggle.

> I've pushed the
> patch.

Thank you!

Laszlo