From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756862AbXLSTtL (ORCPT ); Wed, 19 Dec 2007 14:49:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752709AbXLSTs4 (ORCPT ); Wed, 19 Dec 2007 14:48:56 -0500 Received: from terminus.zytor.com ([198.137.202.10]:44779 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750714AbXLSTs4 (ORCPT ); Wed, 19 Dec 2007 14:48:56 -0500 Message-ID: <4769757E.306@zytor.com> Date: Wed, 19 Dec 2007 11:48:14 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Ingo Molnar CC: Venki Pallipadi , Thomas Gleixner , Len Brown , linux-kernel Subject: Re: [PATCH] x86: Voluntary leave_mm before entering ACPI C3 References: <20071219183443.GA547@linux-os.sc.intel.com> <20071219193255.GA2158@elte.hu> <476972A0.3050105@zytor.com> <20071219194032.GA8849@elte.hu> In-Reply-To: <20071219194032.GA8849@elte.hu> 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 Ingo Molnar wrote: > > i dont think it's required for C3 to even turn off any portion of the > CPU - if an interrupt arrives after the C3 sequence is initiated but > just before dirty cachelines have been flushed then the CPU can just > return without touching anything (such as the TLB) - right? So i dont > think there's any implicit guarantee of TLB flushing (nor should there > be), but in practice, a good C3 sequence would (statistically) turn off > large portions of the CPU and hence the TLB as well. > I think C3 guarantees that the cache contents stay intact, and thus it might make sense in some technology to preserve the TLB as well (being a kind of cache.) Otherwise, what you say here of course is absolutely correct. -hpa