linux-kernel - Re: [PATCH v2 2/3] x86/mm/pat: fix VM

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Date: Wed, 3 Apr 2024 15:12:49 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org, Peter
 Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Thomas
 Gleixner <tglx@...utronix.de>, Christoph Hellwig <hch@....de>, Borislav
 Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski
 <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Fei Li
 <fei1.li@...el.com>, Nathan Chancellor <nathan@...nel.org>, Wupeng Ma
 <mawupeng1@...wei.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 2/3] x86/mm/pat: fix VM_PAT handling in COW mappings

On Wed,  3 Apr 2024 23:21:30 +0200 David Hildenbrand <david@...hat.com> 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@...wei.com>
> Closes: https://lkml.kernel.org/r/20240227122814.3781907-1-mawupeng1@huawei.com
> 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?