[virtio-dev] RE: [virtio-comment] Re: [PATCH 09/11] transport-pci: Describe PCI MMR dev config registers

Parav Pandit
2023-04-14T03:22:30Z

> From: Jason Wang <jasowang@redhat.com>
> Sent: Thursday, April 13, 2023 11:18 PM

> > >
> > > It's a must for ABI and migration compatibility:
> > >
> > > 1) The offset is not necessarily a page boundary
> > > 2) The length is not necessarily times of a PAGE_SIZE
> > > 3) PAGE_SIZE varies among different archs
> > > 4) Two vendors may have two different layout for the structure
> >
> > Migration compatibility check and device composition work will start for
> regular PCI VF in virtio.
> > Two vendors will had some level of programmability as well to make this
> happen.
> > It is orthogonal topic.
>
> Actually not, having new blockers for live migration will complicate the solution
> in the future.
>
It is not a blocker, its just another flexible field that hw vendors will align to a common way to configure.

Just to make sure this is the BAR0 size, right?

> And 1) 2) 3) can happen even if we don't care about migration compatibility,
> no?

I guess one we have spec definition, it wont be a problem.