Re: [PATCH v2 5/8] iommu/arm-smmu-v3: Precompute the invalidation commands

[Mostafa Saleh <smostafa@google.com>]

On Tue, Jul 07, 2026 at 11:58:12AM -0300, Jason Gunthorpe wrote:
> On Tue, Jul 07, 2026 at 11:52:25AM +0000, Mostafa Saleh wrote:
> > On Mon, Jul 06, 2026 at 01:26:42PM -0300, Jason Gunthorpe wrote:
> > > Store the required cmd data in the tlbi and just copy it out when
> > > processing each item in the invs list. The cmd form only depends on
> > > if the instance supports RIL or not, otherwise it is always the same.
> > > 
> > > This avoids redundant calculations for each invs entry.
> > 
> > I do not understand how does this avoids redundant calculation?
> > This would be the case if the domain shares multiple SMMUs,
> > otherwise, a range TLB invalidation should be unique and can not be
> > reused.
> 
> Right, if there are multiple SMMUs for the domain then currently it
> recomputes the range for every one.
> 
> At the moment I think we can't have multiple SMMUs per domain but
> Nioclin has a patch series changing that

Yes, it is not possible at the moment, I think it makes sense to have
it in this series, but a comment would be helpful as it is not clear
from just reading the code.

However, as I mentioned I am not sure if that actually helps on a real
system, is that something that you noticed during perf or based on the
code?

Thanks,
Mostafa

> 
> Jason