Re: [RFC XEN PATCH v2 2/3] x86/pvh: Open PHYSDEVOP_map_pirq for PVH dom0

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

On Fri, Nov 24, 2023 at 06:41:35PM +0800, Jiqian Chen wrote:
> If we run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
> a passthrough device by using gsi, see xen_pt_realize->xc_physdev_map_pirq
> and pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq will
> call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq is not allowed
> because currd is PVH dom0 and PVH has no X86_EMU_USE_PIRQ flag, it will
> fail at has_pirq check.
> 
> So, I think we may need to allow PHYSDEVOP_map_pirq when currd is dom0 (at

And PHYSDEVOP_unmap_pirq also?

> present dom0 is PVH).

IMO it would be better to implement a new set of DMOP hypercalls that
handle the setup of interrupts from physical devices that are assigned
to a guest.  That should allow us to get rid of the awkward PHYSDEVOP
+ XEN_DOMCTL_{,un}bind_pt_irq hypercall interface, which currently
prevents QEMU from being hypervisor version agnostic (since the domctl
interface is not stable).

I understand this might be too much to ask for, but something to take
into account.

Thanks, Roger.