Re: [PATCH v1 1/3] arm64: Add BBM Level 2 cpu feature

[Mikołaj Lenczewski]

On Wed, Feb 19, 2025 at 04:25:56PM +0000, Robin Murphy wrote:
> > On 19/02/2025 15:39, Robin Murphy wrote:
> >> ...
> >>
> >> If this may be used for splitting/compacting userspace mappings, then similarly
> >> to 6e192214c6c8 ("iommu/arm-smmu-v3: Document SVA interaction with new pagetable
> >> features"), strictly we'll also want a check in arm_smmu_sva_supported() to make
> >> sure that the SMMU is OK with BBML2 behaviour too, and disallow SVA if not. Note
> >> that the corresponding SMMUv3.2-BBML2 feature is already strict about TLB
> >> conflict aborts, so is comparatively nice and straightforward.
> 
> Yup, it's really more just a theoretical correctness concern - certainly 
> Arm's implementations from MMU-700 onwards do support BBML2, while 
> MMU-600 is now sufficiently old that nobody is likely to pair it with 
> new BBML-capable CPUs anyway - so it's just to cover the gap that in 
> principle there may be 3rd-party implementations which might get confused.
> 
> Cheers,
> Robin.

Hi Robin,

Thank you for taking the time to review these patches. I will add the
check in the next patch series.

-- 
Kind regards,
Mikołaj Lenczewski