Re: [PATCH v2 2/3] x86/mm/pat: fix VM_PAT handling in COW mappings

[Andrew Morton]

On Wed,  3 Apr 2024 23:21:30 +0200 David Hildenbrand <david@xxxxxxxxxx> wrote:

> PAT handling won't do the right thing in COW mappings: the first PTE
> (or, in fact, all PTEs) can be replaced during write faults to point at
> anon folios. Reliably recovering the correct PFN and cachemode using
> follow_phys() from PTEs will not work in COW mappings.
> 
> ...
> 
> Reported-by: Wupeng Ma <mawupeng1@xxxxxxxxxx>
> Closes: https://lkml.kernel.org/r/20240227122814.3781907-1-mawupeng1@xxxxxxxxxx
> Fixes: b1a86e15dc03 ("x86, pat: remove the dependency on 'vm_pgoff' in track/untrack pfn vma routines")
> Fixes: 5899329b1910 ("x86: PAT: implement track/untrack of pfnmap regions for x86 - v3")

These are really old.  Should we backport this?