linux-kernel - Re: [PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd interfaces

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Date:	Tue, 21 Jul 2015 10:05:44 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@...com>
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, bp@...en8.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, jgross@...e.com,
	konrad.wilk@...cle.com, elliott@...com
Subject: Re: [PATCH v2 0/4] x86, mm: Handle large PAT bit in pud/pmd
 interfaces


* Toshi Kani <toshi.kani@...com> wrote:

> The PAT bit gets relocated to bit 12 when PUD and PMD mappings are used.
> This bit 12, however, is not covered by PTE_FLAGS_MASK, which is corrently
> used for masking pfn and flags for all cases.
> 
> Patch 1/4-2/4 make changes necessary for patch 3/4 to use P?D_PAGE_MASK.
> 
> Patch 3/4 fixes pud/pmd interfaces to handle the PAT bit when PUD and PMD
> mappings are used.
> 
> Patch 3/4 fixes /sys/kernel/debug/kernel_page_tables to show the PAT bit
> properly.
> 
> Note, the PAT bit is first enabled in 4.2-rc1 with WT mappings.

Are patches 1-3 only needed to fix /sys/kernel/debug/kernel_page_tables output, or 
are there other things fixed as well? The patches do not tell us any of that 
information ...

Thanks,

	Ingo
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