linux-kernel - Re: [PATCH] x86/mm/pat: Support splitting of virtual memory areas

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Message-ID: <5bcc86bd-d94d-4f4a-8f4e-81fad78c3e21@intel.com>
Date: Thu, 5 Sep 2024 13:52:40 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Nam Cao <namcao@...utronix.de>, "Liam R. Howlett"
 <Liam.Howlett@...cle.com>, 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>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Vlastimil Babka <vbabka@...e.cz>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, bigeasy@...utronix.de
Subject: Re: [PATCH] x86/mm/pat: Support splitting of virtual memory areas

On 9/5/24 13:08, Nam Cao wrote:
> 
> If I pause this program right after the two mmap(), before any munmap(),
> then:
> $cat /sys/kernel/debug/x86/pat_memtype_list
> PAT memtype list:
> PAT: [mem 0x00000000bffe0000-0x00000000bffe2000] write-back
> PAT: [mem 0x00000000bffe1000-0x00000000bffe2000] write-back
> PAT: [mem 0x00000000fd000000-0x00000000fd002000] uncached-minus <-- what I described
> PAT: [mem 0x00000000fd001000-0x00000000fd003000] uncached-minus <-- what I described
> PAT: [mem 0x00000000febc0000-0x00000000febe0000] uncached-minus

Well, that's not what I had in mind, so I'm obviously the confused one.

Let me take a look through your example and see if I can offer any
alternatives.