Stefano Stabellini <sstabell...@kernel.org> writes: > +Stewart > > On Fri, 8 Dec 2023, Mykyta Poturai wrote: >> Hello everyone, >> >> I am currently working on adding MSI support to virtio-pci on ARM with Xen. > > Excellent! > > >> As far as I understand QEMU Xen ARM machine that is used for >> virtio-pci device emulation does not initialize any interrupt >> controllers. And that makes it somewhat unclear what is the best >> approach to adding the MSI support. So, I would appreciate some >> thoughts on this. >> To trigger the MSI interrupt in Xen guests we basically need to call a >> single DMOP, which I am also implementing. > > You should be able to call xen_inject_msi > > >> So far, I have come up with 3 possible approaches: >> 1. Hooking up the existing GIC code to the Xen Arm machine and extending it >> with the DMOP call. > > No, I would rather avoid this for a couple of reasons. In reality, the > GIC is emulated by Xen, not QEMU. So letting QEMU think that QEMU is > emulating a GIC is more error prone than the alternatives and also it > would allocate resources needlessly. > > >> 2. Writing some new barebones GIC implementation with only the required >> methods (something similar to xen_apic.c). >> 3. Just hooking up the DMOP call to the existing PCI code based on >> xen_enabled() check. > > I would rather not introduce any more if (xen_enabled()) checks beyond > the ones we already have unless it is the only option. So I would go > with option 2). Even better if we could reuse xen_apic.c. xen_apic.c is > just a stub, which is basically the same thing that we need here.
I guess the APIC part of the name is part of the historical baggage of x86 - really it's just a xenpv-irq controller? Anyway yeah I think just move it from hw/i386/xen to hw/xen and maybe give it a new name with an alias to the old one we can deprecate over time? -- Alex Bennée Virtualisation Tech Lead @ Linaro
