linux-kernel - Re: [PATCH v2] x86/mm/pat: (un)track_pfn

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Message-ID: <Z_ZMqPvQTxsyhCa9@gmail.com>
Date: Wed, 9 Apr 2025 12:32:08 +0200
From: Ingo Molnar <mingo@...nel.org>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	kernel test robot <lkp@...el.com>,
	Dan Carpenter <error27@...il.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Rik van Riel <riel@...riel.com>, "H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2] x86/mm/pat: (un)track_pfn_copy() fix + doc
 improvements


* David Hildenbrand <david@...hat.com> wrote:

> We got a late smatch warning and some additional review feedback.
> 
> 	smatch warnings:
> 	mm/memory.c:1428 copy_page_range() error: uninitialized symbol 'pfn'.
> 
> We actually use the pfn only when it is properly initialized; however,
> we may pass an uninitialized value to a function -- although it will not
> use it that likely still is UB in C.
> 
> So let's just fix it by always initializing pfn in the caller of
> track_pfn_copy(), and improving the documentation of track_pfn_copy().
> 
> While at it, clarify the doc of untrack_pfn_copy(), that internal checks
> make sure if we actually have to untrack anything.

Note that the title isn't accurate anymore, it's not an 'x86/mm/pat' 
patch, but an 'mm' patch.

Thanks,

	Ingo