linux-kernel - Re: [RFC PATCH 0/11] Support Write-Through mapping on x86

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Message-ID: <53CD443A.6050804@zytor.com>
Date:	Mon, 21 Jul 2014 09:47:54 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Toshi Kani <toshi.kani@...com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org,
	arnd@...db.de, plagnioj@...osoft.com, tomi.valkeinen@...com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	stefan.bader@...onical.com, luto@...capital.net, airlied@...il.com,
	bp@...en8.de
Subject: Re: [RFC PATCH 0/11] Support Write-Through mapping on x86

On 07/21/2014 09:31 AM, Toshi Kani wrote:
> Do you have any comments / suggestions for this approach?

Approach to what, specifically?

Keep in mind the PAT bit is different for large pages.  This needs to be
dealt with.  I would also like a systematic way to deal with the fact
that Xen (sigh) is stuck with a separate mapping system.

I guess Linux could adopt the Xen mappings if that makes it easier, as
long as that doesn't have a negative impact on native hardware -- we can
possibly deal with some older chips not being optimal.  However, my
thinking has been to have a "reverse PAT" table in memory of memory
types to encodings, both for regular and large pages.

	-hpa

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