linux-kernel - Re: [PATCH] mm/autonuma: don't use set_pte

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Message-ID: <20170206222642.u2e5ip4h2udaehr4@techsingularity.net>
Date:   Mon, 6 Feb 2017 22:26:42 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:     akpm@...ux-foundation.org, Rik van Riel <riel@...riel.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/autonuma: don't use set_pte_at when updating protnone
 ptes

On Mon, Feb 06, 2017 at 10:36:16PM +0530, Aneesh Kumar K.V wrote:
> Architectures like ppc64, use privilege access bit to mark pte non accessible.
> This implies that kernel can do a copy_to_user to an address marked for numa fault.
> This also implies that there can be a parallel hardware update for the pte.
> set_pte_at cannot be used in such scenarios. Hence switch the pte
> update to use ptep_get_and_clear and set_pte_at combination.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

Yeah, ok. The main thing is that it still avoids doing an unnecessary TLB
flush so

Acked-by: Mel Gorman <mgorman@...hsingularity.net>

-- 
Mel Gorman
SUSE Labs