Re: [PATCH v2] iommu/arm-smmu-v3: Match Stall behaviour for S2

[Jason Gunthorpe]

On Thu, Aug 15, 2024 at 02:41:52PM +0100, Robin Murphy wrote:

> Unfortunately we can't do that, because there *are* RCiEP devices whose data
> interfaces are native AMBA, and thus for whom stalling is not actually a
> protocol violation as it would be on a real PCIe transport layer;
> correspondingly, it's *because* they are not true PCIe devices that they
> can't support ATS, and thus need stall support in order to do SVA, so things
> should still work out OK in practice.

I wondered if that would be the case.

Looks like if we want to do anything then arm_smmu_ats_supported()
would be the right place.

> >          if (dev_is_pci(dev)) {
> > 
> > Though I have no idea how the GPU driver that wants to use this
> > works - it doesn't seem to be intree :\
> 
> It's not a GPU: drivers/crypto/hisilicon/zip/

Ohhhh.. so it goes through uacce, I see.

Jason