Subject: Re: [PATCH 0/3] virtio-net: inline header support

From: Rusty Russell <[email-masked]>
Date: Fri, 12 Oct 2012 09:07:46 +1030

"Michael S. Tsirkin" <[email-masked]> writes:
> On Thu, Oct 11, 2012 at 10:33:31AM +1030, Rusty Russell wrote:
>> OK.  Well, Anthony wants qemu to be robust in this regard, so I am
>> tempted to rework all the qemu drivers to handle arbitrary layouts.
>> They could use a good audit anyway.
>
> I agree here. Still trying to understand whether we can agree to use
> a feature bit for this, or not.

I'd *like* to imply it by the new PCI layout, but if it doesn't work
we'll add a new feature bit.

I'm resisting a feature bit, since it constrains future implementations
which could otherwise assume it.

>> This would become a glaring exception, but I'm tempted to fix it to 32
>> bytes at the same time as we get the new pci layout (ie. for the virtio
>> 1.0 spec).
>
> But this isn't a virtio-pci only issue, is it?
> qemu has s390 bus with same limmitation.
> How can we tie it to pci layout?

They can use a transport feature if they need to, of course.  But
perhaps the timing with ccw will coincide with the fix, in which they
don't need to, but it might be a bit late.

Cornelia?

Cheers,
Rusty.