Re: [PATCH RFC 2/2] iommu/arm-smmu-v3: Bypass SID0 for NXP i.MX95

From: Robin Murphy
Date: Tue Oct 15 2024 - 11:13:27 EST


On 2024-10-15 1:47 pm, Jason Gunthorpe wrote:
On Tue, Oct 15, 2024 at 08:13:28AM +0000, Pranjal Shrivastava wrote:

Umm.. this was specific for rmr not a generic thing. I'd suggest to
avoid meddling with the STEs directly for acheiving bypass. Playing
with the iommu domain type could be neater. Perhaps, modify the
ops->def_domain_type to return an appropriate domain?

Yeah, that is the expected way, to force the def_domain_type to
IDENTITY and refuse to attach a PAGING/BLOCKED domain.

There is no domain, this is bypassing an arbitrary StreamID not associated with any device. Which incidentally is something an IORT RMR can quite happily achieve already (I think the DT reserved-memory binding does need a proper device node to relate to, though).

Thanks,
Robin.