From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752791AbaCJXE2 (ORCPT ); Mon, 10 Mar 2014 19:04:28 -0400 Received: from mga09.intel.com ([134.134.136.24]:27698 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752110AbaCJXE1 (ORCPT ); Mon, 10 Mar 2014 19:04:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,627,1389772800"; d="scan'208";a="489408106" Message-ID: <531E4488.2000400@linux.intel.com> Date: Mon, 10 Mar 2014 16:02:32 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Linus Torvalds , Stefani Seibold CC: Andy Lutomirski , Linux Kernel Mailing List , Andreas Brief , Martin Runge Subject: Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000 References: <20140307013833.GD8427@localhost> <1394176888.1018.3.camel@wall-e.seibold.net> <1394229220.20013.13.camel@wall-e.seibold.net> <1394354848.1002.37.camel@wall-e.seibold.net> <531D044C.2090303@linux.intel.com> <531DD35A.5060202@linux.intel.com> <1394481804.980.9.camel@wall-e.seibold.net> <531E1B53.5090205@linux.intel.com> <20140310222528.Horde.tMG70UcHgBuz9DV3W9_aaA1@webmail.your-server.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/10/2014 02:39 PM, Linus Torvalds wrote: > On Mon, Mar 10, 2014 at 2:25 PM, wrote: >> >> This was discovered by me. > > Sorry for the misattribution. > >> But this is not a real solution, at least when vcpu function support >> will be added, then the code size will exceed the page size. Reserving >> two pages for the VDSO is a good option. > > Quite frankly, there is no way in hell I will take a patch like that > for 3.14 any more, and I would argue against it for stable. > > Now, if this problem never happens with current kernels (because it's > purely due to the patch in -tip), then I don't much care. > It is only for tip:x86/vdso, so current kernels don't matter. There is going to be 32-bit use in the embedded sector for a long time to come, I suspect/fear, so I'm not opposed to giving it a bit of a performance boost as long as it isn't too invasive. I think Andy's commentary applies, though :) > IMO this is dumb. I can think of two sensible solutions: > > 1. Get rid of compat vdso and replace it with no vdso at all. This is > compatible with everything and requires almost no code > > 2. Fix compat vdso. Give it as much space as needed, make the address > dynamic, and relocate it to the right place. -hpa