linux-kernel - Re: [patch]pageattr: cache flush before tlb flush

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Message-ID: <877iad1pcr.fsf@basil.nowhere.org>
Date:	Tue, 19 Aug 2008 08:38:28 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: Re: [patch]pageattr: cache flush before tlb flush

Shaohua Li <shaohua.li@...el.com> writes:

> clflush uses a virtual address but cache line is physical indexed in
> x86. In my understanding, clflush will do some pagetable walk, so doing
> cache flush first should reduce some pagetable walk.

The SDM describes the exact sequence how this should be done.
Linux unfortunately skips one step currently, but it's not a good
idea to diverge even more.

-Andi
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