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

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jan 13, 2026 at 04:51:12PM -0400, Jason Gunthorpe wrote:
> > -       safe_bits[1] |= cpu_to_le64(STRTAB_STE_1_EATS);
> > +       if (!((cur[2] | target[2]) & cpu_to_le64(STRTAB_STE_2_S2S)))
> > +               safe_bits[1] |= cpu_to_le64(
> > +                       FIELD_PREP(STRTAB_STE_1_EATS, STRTAB_STE_1_EATS_TRANS));
> > --------------------------------------------------------------------------
> > 
> > @will, does this look good to you? I can send a v7 with this.
> 
> That is an easy way to address Will's observation, makes sense to me.

Ah, but it looks like it can generate an errant view of a EATS that is
neither old or new. Ie value 3, reserved.

I think you should just check if old or new has EATS bit 1 set:

if (!((cur[2] | target[2]) & cpu_to_le64(STRTAB_STE_2_S2S)) &&
    !((cur[1] | target[1]) & cpu_to_le64(FIELD_PREP(STRTAB_STE_1_EATS, 2))))

Which the current driver never does..

Jason