Re: [PATCH rc v5 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence

[Jason Gunthorpe]

On Wed, Jan 07, 2026 at 09:20:06PM +0000, Will Deacon wrote:
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  2 ++
> >  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c  | 18 ++++++++++---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 27 ++++++++++++++-----
> >  3 files changed, 37 insertions(+), 10 deletions(-)
> 
> Hmm. So this appears to ignore the safe bits entirely, whereas the
> rationale for the change is that going from {MEV,EATS} disabled to
> enabled is safe (which I agree with). 

The argument was it doesn't matter for either direction be it disabled
to enabled or vice versa, see my reply to Mustfa in the v4 posting:

https://lore.kernel.org/all/20251218180129.GA254720@xxxxxxxxxx/

> So what prevents an erroneous hitless STE update when going from
> {MEV,EATS} enabled to disabled after this change?

Nothing, it isn't erroneous.

Jason