Re: [PATCH v6 09/10] iommu/arm-smmu-v3: Skip cd sync if CD table isn't active

[Will Deacon]

On Mon, Aug 21, 2023 at 06:16:08PM +0800, Michael Shavit wrote:
> On Wed, Aug 16, 2023 at 9:20 PM Michael Shavit <mshavit@xxxxxxxxxx> wrote:
> >
> > This commit explicitly keeps track of whether a CD table is installed in
> > an STE so that arm_smmu_sync_cd can skip the sync when unnecessary. This
> > was previously achieved through the domain->devices list, but we are
> > moving to a model where arm_smmu_sync_cd directly operates on a master
> > and the master's CD table instead of a domain.
> >
> > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > Reviewed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Signed-off-by: Michael Shavit <mshavit@xxxxxxxxxx>
> > ---
> > Happy to drop this commit if we don't think it's useful.
> 
> Hi Will,
> Do you have any recommendations for keeping or dropping this commit in
> the end? It's only purpose is to minimize any potential performance
> impact from the refactor but can certainly be dropped if you don't
> think it's worth the complication.

I'd prefer to drop it unless somebody can measure the benefits that it
brings.

Will