From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934561AbYBHLJV (ORCPT ); Fri, 8 Feb 2008 06:09:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759616AbYBHLJN (ORCPT ); Fri, 8 Feb 2008 06:09:13 -0500 Received: from one.firstfloor.org ([213.235.205.2]:44930 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759473AbYBHLJM (ORCPT ); Fri, 8 Feb 2008 06:09:12 -0500 Date: Fri, 8 Feb 2008 12:44:19 +0100 From: Andi Kleen To: Ingo Molnar Cc: Andi Kleen , davej@codemonkey.org.uk, tglx@linutronix.de, linux-kernel@vger.kernel.org, "H. Peter Anvin" Subject: Re: [PATCH] Use global TLB flushes in MTRR code Message-ID: <20080208114419.GB4745@one.firstfloor.org> References: <20080207190241.GA9449@basil.nowhere.org> <20080207191337.GA13111@elte.hu> <20080207200308.GA26555@one.firstfloor.org> <20080207203705.GA19083@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080207203705.GA19083@elte.hu> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > because it's not just an open-coded __tlb_flush_all(), it _disables PGE > and keeps it so while the MTRR's are changed on all CPUs_. Yes and? > > Your patch adds __flush_tlb_all() which re-enables the PGE bit in cr4, > see asm-x86/tlbflush.h: > > /* clear PGE */ > write_cr4(cr4 & ~X86_CR4_PGE); > /* write old PGE again and flush TLBs */ > write_cr4(cr4); > > so we'll keep PGE enabled during the MTRR setting - which changes > behavior. It changes behaviour in some minor ways but I don't think it makes any difference. PGE only influences TLB flushes (according to its specification) and all the TLB flushes still run with PGE disabled. -Andi