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 S1754828AbaCMSJh (ORCPT <rfc822;w@1wt.eu>);
	Thu, 13 Mar 2014 14:09:37 -0400
Received: from terminus.zytor.com ([198.137.202.10]:41320 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1754485AbaCMSJg (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 13 Mar 2014 14:09:36 -0400
Message-ID: <5321F418.1030304@zytor.com>
Date: Thu, 13 Mar 2014 11:08:24 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0
MIME-Version: 1.0
To: Andy Lutomirski <luto@amacapital.net>
CC: Stefani Seibold <stefani@seibold.net>,
        Greg KH <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        X86 ML <x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        John Stultz <john.stultz@linaro.org>,
        Pavel Emelyanov <xemul@parallels.com>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        andriy.shevchenko@linux.intel.com,
        Martin Runge <Martin.Runge@rohde-schwarz.com>,
        Andreas Brief <Andreas.Brief@rohde-schwarz.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 3/3] x86, vdso32: handle 32 bit vDSO larger one page
References: <1394664680-17799-1-git-send-email-stefani@seibold.net> <1394664680-17799-4-git-send-email-stefani@seibold.net> <5320E689.7060607@zytor.com> <CALCETrXQJvkk-5ncSgTyoy9sCN0AT+h9-1F6wAnxqRm242PjrQ@mail.gmail.com> <5321D45C.7040504@zytor.com> <CALCETrVy3oW=qvJWbGtKTZ=0dZLjHtmBphPDnP1N8nLmXc=+9A@mail.gmail.com>
In-Reply-To: <CALCETrVy3oW=qvJWbGtKTZ=0dZLjHtmBphPDnP1N8nLmXc=+9A@mail.gmail.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 03/13/2014 10:28 AM, Andy Lutomirski wrote:
> 
> Does this mean you prefer the relocation approach to the compat vdso
> removal approach?  It seems like Linus is okay with either one.
> 

Actually, thinking about it, removing it is probably better:

a) gets rid of legacy code, making room for unification;
b) either way enabling compat support (either relocation or disabling
   the vdso) has a performance penalty for *all* processes.

The only way to avoid that is to have a vdso at a fixed addresses across
all processes, either in the fixmap or in the user area (presumably at
the very top.)

	-hpa