Re: [PATCH v6 08/12] fork: Clear PASID for new mm

[Jean-Philippe Brucker]

On Mon, Mar 01, 2021 at 03:00:11PM -0800, Jacob Pan wrote:
> > functionality is not a problem without this patch on x86. But I think
> I feel the reason that x86 doesn't care is that mm->pasid is not used
> unless bind_mm is called.

I think vt-d also maintains the global_svm_list, that tells whether a
PASID is already allocated for the mm. The SMMU driver relies only on
iommu_sva_alloc_pasid() for this.

> For the fork children even mm->pasid is non-zero,
> it has no effect since it is not loaded onto MSRs.
> Perhaps you could also add a check or WARN_ON(!mm->pasid) in load_pasid()?
> 
> > we do need to have this patch in the kernel because PASID is per addr
> > space and two addr spaces shouldn't have the same PASID.
> > 
> Agreed.
> 
> > Who will accept this patch?

It's not clear from get_maintainers.pl, but I guess it should go via
linux-mm. Since the list wasn't cc'd on the original patch, I resent it.

Thanks,
Jean