Re: [PATCH v4 2/4] vhost-vsock-pci: force virtio version 1

[Stefano Garzarella]

On Mon, Sep 21, 2020 at 11:46:02AM +0200, Cornelia Huck wrote:
> On Mon, 21 Sep 2020 10:38:05 +0200
> Stefano Garzarella <sgarzare@redhat.com> wrote:
> 
> > Commit 9b3a35ec82 ("virtio: verify that legacy support is not
> > accidentally on") added a safety check that requires to set
> > 'disable-legacy=on' on vhost-vsock-pci device:
> > 
> >     $ ./qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=5
> >         qemu-system-x86_64: -device vhost-vsock-pci,guest-cid=5:
> >         device is modern-only, use disable-legacy=on
> > 
> > virtio-vsock was introduced after the release of VIRTIO 1.0
> > specifications, so it should be 'modern-only'.
> > In addition Cornelia verified that forcing a legacy mode on
> > vhost-vsock-pci device using x86-64 host and s390x guest, so with
> > different endianness, produces strange behaviours.
> > 
> > This patch forces virtio version 1 and removes the 'transitional_name'
> > property removing the need to specify 'disable-legacy=on' on
> > vhost-vsock-pci device.
> > 
> > To avoid migration issues, we force virtio version 1 only when
> > legacy check is enabled in the new machine types (>= 5.1).
> 
> Maybe add
> 
> "As the transitional device name is not commonly used, we do not
> provide compatibility handling for it." ?

Yes, I'll add in v5.

> 
> > 
> > Cc: qemu-stable@nongnu.org
> > Reported-by: Qian Cai <caiqian@redhat.com>
> > Reported-by: Qinghua Cheng <qcheng@redhat.com>
> > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1868449
> > Suggested-by: Cornelia Huck <cohuck@redhat.com>
> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > ---
> > v3:
> >  - forced virtio version 1 only with new machine types
> > v2:
> >  - fixed commit message [Cornelia]
> > ---
> >  hw/virtio/vhost-vsock-pci.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> 
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Thanks,
Stefano