Re: [PATCH v2 14/18] iommu/arm-smmu-v3: Support domains with shared CDs

[Michael Shavit]

On Wed, Jun 14, 2023 at 5:17 PM Michael Shavit <mshavit@xxxxxxxxxx> wrote:
> The arm-smmu-v3-sva.c implementation avoids all these problems because it
> doesn't need to allocate an io_pgtable; the shared arm_smmu_ctx_desc's
> TTBR is set to the MM's TTBR. One possible solution would be to make
> the changes proposed in 1., but only allowing SVA domains to attach to
> multiple devices:
> 1. Domain functions only accessed by arm-smmu-v3.c (such as
> arm_smmu_iova_to_phys) can assume there's a single
> arm_smmu_device_domain per arm_smmu_domain.
> 2. Domain functions also accessed by arm-smmu-v3-sva.c (such as
> invalidations commands) must iterate over all arm_smmu_device_domains.

Or rather, arm_smmu_domain would hold a list of attached smmu devices,
but only SVA domains would be allowed to have multiple entries in that
list since the other arm_smmu_domain fields are tied to a single SMMU
device for other domain types.