On 6/16/25 09:20, Jason Gunthorpe wrote:
On Sun, Jun 15, 2025 at 02:47:15PM -0400, Demi Marie Obenour wrote:
Is a paravirtualized IOMMU with interrupt remapping something that makes sense?
IMHO linking interrupt remapping to the iommu is a poor design, interrupt routing belongs in the irq subsystem, not in the iommu.
I agree.
The fact AMD and Intel both coupled their interrupt routing to their iommu hardware is just a weird design decision. ARM didn't do this, for instance.
Arm did the right thing here, IMO.
So I would not try to do this at all, you should have a para-virtualized IRQ interface, not an extension to virtio-iommu adding interrupt handling. :\
I don't disagree at all.
AFAIK hyperv shows how to build something like this. Would this need KVM patches? I'm concerned that implementing this in userspace would interact badly with the irqfd fast path. -- Sincerely, Demi Marie Obenour (she/her/hers)