Re: [PATCH v2 4/8] iommu/arm-smmu-v3: move stall_enabled to the cd table

From: Michael Shavit
Date: Tue Aug 01 2023 - 04:10:33 EST

> On Mon, Jul 31, 2023 at 09:28:40PM -0700, Nicolin Chen wrote:
> > This cd_table->stall_enabled comes from master->stall_enabled, and
> > cd_table will be in master structure. Also, struct arm_smmu_master
> > pointer will be passed in to arm_smmu_write_ctx_desc(). So, there
> > seems to be no need of master->cd_table.stall_enabled in the end;
> > just use master->stall_enabled directly?

Yes it's correct that this change isn't strictly necessary. Thoughts jgg@ ?

On Tue, Aug 1, 2023 at 12:52 PM Nicolin Chen <nicolinc@xxxxxxxxxx> wrote:
> Actually the stall_enabled might still need to be per-CD/domain.
> If a domain is attached by two masters. The domain->stall_enabled
> is initialized with the first master->stall_enabled. Then, the
> second master->stall_enabled would be required to match with the
> domain->stall_enabled. arm_smmu_attach_dev() has such a sanity.
> So, I think we might not need this patch.

But why force domains attached to different masters to have the same
stall_enabled setting? Whether stall is enabled is strictly a property
of the master, not the domain. IMO the fact that it was stored in
domain and checked in attach_dev was only because the previous design
required it, not because it's more appropriate.