Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756565AbYAZBNt (ORCPT ); Fri, 25 Jan 2008 20:13:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754103AbYAZBNk (ORCPT ); Fri, 25 Jan 2008 20:13:40 -0500 Received: from terminus.zytor.com ([198.137.202.10]:37305 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753984AbYAZBNj (ORCPT ); Fri, 25 Jan 2008 20:13:39 -0500 Message-ID: <479A883A.50001@zytor.com> Date: Fri, 25 Jan 2008 17:09:14 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Keir Fraser , Ingo Molnar , LKML , Andi Kleen , Jan Beulich , Eduardo Pereira Habkost , Ian Campbell , William Irwin , Linus Torvalds Subject: Re: [PATCH 11 of 11] x86: defer cr3 reload when doing pud_clear() References: <479A7A88.6010505@zytor.com> <479A858B.6070102@goop.org> In-Reply-To: <479A858B.6070102@goop.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1230 Lines: 27 Jeremy Fitzhardinge wrote: > >> Now, all of this reminds me of something somewhat messy: if we share >> the kernel page tables for trampoline page tables, as discussed >> elsewhere, we HAVE to do a complete, all-tlb-including-global-pages >> flush after use, since the kernel pages are global and otherwise will >> stick around. Unlike the permissions pages, there aren't G enable >> bits on the higher levels, but only for the PTEs themselves. > > That wouldn't happen to often though, would it. The identity mapping is > only interested in a 1:1 view on RAM, and that's not going to change at > all? Does the TLB cache PAT attributes? Do you need to do a global > flush after changing a PTE's PAT bits to make sure that all that PTE's > mappings have a consistent view on memory? > You do need to flush *that page* globally, yes. As far as flushing after using the trampoline pagetables, we're talking about rare, expensive events here like suspend to ram. -hpa -- 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/