Re: [XEN PATCH v12 2/7] x86/pvh: Allow (un)map_pirq when dom0 is PVH

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Jul 31, 2024 at 11:02:01AM +0200, Jan Beulich wrote:
> On 31.07.2024 10:51, Roger Pau Monné wrote:
> > I agree with (a), but I don't think enabling PVH dom0 usage of the
> > hypercalls should be gated on this.  As said a PV dom0 is already
> > capable of issuing PHYSDEVOP_{,un}map_pirq operations against a PVH
> > domU.
> 
> Okay, I can accept that as an intermediate position. We ought to deny
> such requests at some point though for PVH domains, the latest in the
> course of making vPCI work there.

Hm, once physdev_map_pirq() works as intended against PVH domains, I
don't see why we would prevent the usage of PHYSDEVOP_{,un}map_pirq
against such domains.

Granted using vPCI for plain PCI passthrough is the best option, but I
also don't think we should limit it in the hypervisor.  Some kind of
passthrough (like when using vfio/mdev) will still need something akin
to a device model I would expect.

Thanks, Roger.