Re: [PATCH] pc-bios/s390-ccw: Use memory barriers in virtio code

[Thomas Huth]

On 16/02/2021 15.32, Peter Maydell wrote:
> On Tue, 16 Feb 2021 at 14:30, Cornelia Huck <cohuck@redhat.com> wrote:
> > Step 4 in "2.7.13 Supplying Buffers to The Device":
> >
> > "The driver performs a suitable memory barrier to ensure the device
> > sees the updated descriptor table and available ring before the next
> > step."
>
> I thought that my first time through the spec as well, but
> I think the whole of section 2.7 is dealing with "packed virtqueues",
> which have to be explicitly negotiated and which I don't think
> the s390-ccw code is doing.

Right. I think the s390-ccw code is still based on virtio v1.0, that's why I 
also only looked at that version of the spec.

 Thomas