Re: [PATCH-for-9.0 v2 06/19] hw/pci/msi: Restrict xen_is_pirq_msi() call to Xen

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On 14 November 2023 09:38:02 GMT-05:00, "Philippe Mathieu-Daudé" 
<philmd@xxxxxxxxxx> wrote:
>Similarly to the restriction in hw/pci/msix.c (see commit
>e1e4bf2252 "msix: fix msix_vector_masked"), restrict the
>xen_is_pirq_msi() call in msi_is_masked() to Xen.
>
>Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>

Hm, we do also support the Xen abomination of snooping on MSI table writes to 
see if they're targeted at a Xen PIRQ, then actually unmasking the MSI from 
QEMU when the guest binds the corresponding event channel to that PIRQ.

I think this is going to break in CI as kvm_xen_guest.py does deliberately 
exercise that use case, doesn't it?

I deliberately *didn't* switch to testing the Xen PV net device, with a comment 
that testing MSI and irqchip permutations was far more entertaining. So I hope 
it should catch this?