Re: [PATCH 0/7] Enable Qualcomm WiFi PCIe passthrough to VMs

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Oct 13, 2026 at 03:43:13PM +0200, Jose Ignacio Tornos Martinez wrote:
> Hi Jason,
> 
> I understand the concern about compatibility implications, but to
> clarify, my intention is not to create an ABI or a "MSI caching
> concept". 

It very much is an ABI, you defined a new ABI in the config space a
layout between guest and host that we have to maintain forever.

Just for a hacky solution, it is not so nice.

> I can explore converting ath11k/ath12k to
> platform_device_msi_init_and_alloc_irqs(). However, if I understood
> correctly, the VM problem remains identical after that change — the
> firmware still needs physical host addresses, and device MSI domains
> in the VM would still provide virtual ones.

Yes, but it removes the solution of copying data from the existing
MSI-X table from consideration, which is the primary hacky thing here.

> I'm happy to do this refactoring if it opens a path to get these
> devices working in VMs. What VM mechanism would you accept for
> exposing physical MSI values through device MSI domains?

Once you have a MSI domain you just need a driver wired into it that
can request and get the physical addresses from the hypervisor. Then
when that domain is in use the guest will always see true physical.

That part is easy enough, it already exists and you don't need any
driver changes.

The bit that isn't clear is how you get the domain in the first
place. I suppose something like a virtio-msi is a good starting point,
but I don't know enough about ACPI/etc to imagine how to wire it into
the flow.

IIRC hyperv does this, so maybe there is something to follow there..

> Jeff is escalating to Qualcomm engineering again (thank you for
> that), but users with deployed hardware need something working in a
> reasonable timeframe.

Yes, but it has already been years, and Qualcomm doesn't seem to care
about these uses cases, so I'm not sure I see the urgency to do a bad
ABI hack..

Jason