Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753214Ab2BUTvp (ORCPT ); Tue, 21 Feb 2012 14:51:45 -0500 Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:59316 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752113Ab2BUTvn convert rfc822-to-8bit (ORCPT ); Tue, 21 Feb 2012 14:51:43 -0500 MIME-Version: 1.0 In-Reply-To: <4F43F54D.50201@zytor.com> References: <1329696488-16970-1-git-send-email-hpa@zytor.com> <1329696488-16970-31-git-send-email-hpa@zytor.com> <4F42E171.9080005@mit.edu> <4F431665.3010004@zytor.com> <4F43D98D.1020406@zytor.com> <4F43EA83.6020203@zytor.com> <4F43F25E.3030004@zytor.com> <4F43F54D.50201@zytor.com> From: Andrew Lutomirski Date: Tue, 21 Feb 2012 11:51:23 -0800 X-Google-Sender-Auth: HFv-ZLPlgae977BVZho1oAkgDnM Message-ID: Subject: Re: [PATCH 30/30] x32: Add x32 VDSO support To: "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, hjl.tools@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1344 Lines: 33 On Tue, Feb 21, 2012 at 11:49 AM, H. Peter Anvin wrote: > On 02/21/2012 11:40 AM, Andrew Lutomirski wrote: >>> >>> I was having delusions that we could have a task-owned PDT in negative >>> space, but that would require unsharing the third level, too, which is >>> just way too messy. >> >> I'd like to do that, too, and I'd also like to have a per-cpu >> kernel-only page in there, but that's even worse. ?If we had a >> separate cr3-like register for negative addresses, life would be good >> :) >> > > No, that wouldn't help. ?The situation is actually quite similar to the > current situation where we have an unshared fourth level, but since the > fourth entries are 512G per entry, we would have to push unsharing of > the kernel address space at least one more level (1G), possibly two > (2M). ?Painful. > > The main advantage of a separate cr3 would be that we wouldn't need the > unshared top level for the kernel side. Also, as is, if the top level wants to be per-cpu *and* per-task, that's a big explosion of page tables that all need to stay in sync. Oh well. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/