From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932827Ab3LDQDE (ORCPT <rfc822;w@1wt.eu>);
	Wed, 4 Dec 2013 11:03:04 -0500
Received: from terminus.zytor.com ([198.137.202.10]:58682 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932602Ab3LDQDC (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 4 Dec 2013 11:03:02 -0500
Message-ID: <529F51D9.7010001@zytor.com>
Date: Wed, 04 Dec 2013 08:01:29 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
MIME-Version: 1.0
To: Oleg Nesterov <oleg@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
CC: Hugh Dickins <hughd@google.com>, Peter Zijlstra <peterz@infradead.org>,
        Jiri Kosina <jkosina@suse.cz>, Andi Kleen <andi@firstfloor.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Andi Kleen <ak@linux.intel.com>, Ingo Molnar <mingo@kernel.org>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH?] uprobes: change uprobe_write_opcode() to modify the
 page directly
References: <CA+55aFxJGidV4=ot0z_Va8+y2QWTDYghTm1Gin84StZ+R1SfXg@mail.gmail.com> <20131203184909.GA17571@redhat.com> <CA+55aFw3N=iNW2Ej6w7oksX5JDVis7QL=9X9D7JB_tKZhrjsLw@mail.gmail.com> <529E2F0C.8070405@zytor.com> <20131203200147.GB19083@redhat.com> <529E3D4C.9070403@zytor.com> <20131203203826.GA24812@redhat.com> <e6082bc4-c910-4a36-9e40-624b9319f5fb@email.android.com> <20131203205400.GA25735@redhat.com> <CA+55aFxKk+O4e51sq6iqunVWAwKfNAnZ-3=aZT-VuRpDAZUnzQ@mail.gmail.com> <20131204111125.GA26552@redhat.com>
In-Reply-To: <20131204111125.GA26552@redhat.com>
X-Enigmail-Version: 1.6
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 12/04/2013 03:11 AM, Oleg Nesterov wrote:
> 
> It is still not clear to me if we can simply change a single byte on
> x86 or not, but at least on powerpc we need to update 4 bytes. Perhaps
> we can conditionalize these pte games later.
> 

But 4 aligned bytes can be written as a single transaction.

	-hpa