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

Jason Wang
2023-04-10T06:20:33Z

On Mon, Apr 10, 2023 at 2:15 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Apr 10, 2023 at 09:33:32AM +0800, Jason Wang wrote:
> > This is fine for vDPA but not for virtio if the design can only work
> > for some specific setups (OSes/archs).
> >
> > Thanks
>
> Well virtio legacy has a long history of documenting existing hacks :)

Exactly, so the legacy behaviour is not (or can't be) defined by the
spec but the codes.

> But yes, VIRTIO_F_ORDER_PLATFORM has to be documented.
> And we have to decide what to do about ACCESS_PLATFORM since
> there's a security problem if device allows not acking it.
> Two options:
> - relax the rules a bit and say device will assume ACCESS_PLATFORM
> is acked anyway

This will break legacy drivers which assume physical addresses.

> - a new flag that is insecure (so useful for sec but useless for dpdk) but optional

This looks like a new "hack" for the legacy hacks.

And what about ORDER_PLATFORM, I don't think we can modify legacy drivers...

Thanks

>
> --
> MST