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Date: Wed, 3 Apr 2024 15:12:49 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, Peter
 Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, Thomas
 Gleixner <tglx@linutronix.de>, Christoph Hellwig <hch@lst.de>, Borislav
 Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski
 <luto@kernel.org>, Dave Hansen <dave.hansen@linux.intel.com>, Fei Li
 <fei1.li@intel.com>, Nathan Chancellor <nathan@kernel.org>, Wupeng Ma
 <mawupeng1@huawei.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2 2/3] x86/mm/pat: fix VM_PAT handling in COW mappings
Message-Id: <20240403151249.0f4fc5b4f8c07630fbbb6338@linux-foundation.org>
In-Reply-To: <20240403212131.929421-3-david@redhat.com>
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	<20240403212131.929421-3-david@redhat.com>
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On Wed,  3 Apr 2024 23:21:30 +0200 David Hildenbrand <david@redhat.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@huawei.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?