From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yinghai Lu" Subject: Re: [linux-pm] [RFC PATCH 0/4] save and restore ACPI NVS memory during hibernation Date: Fri, 11 Jul 2008 14:56:17 -0700 Message-ID: <86802c440807111456k5d46a46co18bee343541fed8c@mail.gmail.com> References: <1215051868.5628.32.camel@rzhang-dt.sh.intel.com> <200807112118.35562.rjw@sisk.pl> <20080711205253.GI6843@elf.ucw.cz> <200807112259.56263.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from rv-out-0506.google.com ([209.85.198.235]:33596 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754737AbYGKV4S (ORCPT ); Fri, 11 Jul 2008 17:56:18 -0400 Received: by rv-out-0506.google.com with SMTP id k40so4567960rvb.1 for ; Fri, 11 Jul 2008 14:56:17 -0700 (PDT) In-Reply-To: <200807112259.56263.rjw@sisk.pl> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: Pavel Machek , Zhang Rui , linux-pm , linux-acpi , linux-kernel On Fri, Jul 11, 2008 at 1:59 PM, Rafael J. Wysocki wrote: > On Friday, 11 of July 2008, Pavel Machek wrote: >> On Fri 2008-07-11 21:18:34, Rafael J. Wysocki wrote: >> > On Friday, 11 of July 2008, Pavel Machek wrote: >> > > On Wed 2008-07-09 21:37:18, Rafael J. Wysocki wrote: >> > > > On Tuesday, 8 of July 2008, Pavel Machek wrote: >> > > > > Hi! >> > > > > >> > > > > > According to the ACPI spec, ACPI NVS memory region is required to >> > > > > > be saved/restored by OS during hibernation. >> > > > > > >> > > > > > Section 15.3.2 ACPI Spec 3.0b, >> > > > > > "OSPM will call the _PTS control method some time before entering >> > > > > > a sleeping state, to allow the platform???s AML code to update >> > > > > > this memory image before entering the sleeping state. >> > > > > > After the system awakes from an S4 state, OSPM will restore this >> > > > > > memory area and call the _WAK control method to enable the BIOS >> > > > > > to reclaim its memory image." >> > > > > > >> > > > > > This patch set add the mechanism to save/restore ACPI NVS memory >> > > > > > during hibernation. >> > > > > > >> > > > > > Patch 01: call platform_begin before swsusp_shrink_memory. >> > > > > > So that we can allocate enough pages for ACPI NVS memory >> > > > > > before shrink the memory. >> > > > > >> > > > > Why is it neccessary to allocate memory for a copy? We should be able >> > > > > to save ACPI NVS area same way we are saving kernel pages, no? >> > > > >> > > > Because we want to restore it from the hibernated kernel (when it gets control >> > > > back again). >> > > >> > > Why is that important? So we can run some ACPI methods from hibernated >> > > kernel before restoring it? >> > >> > We're supposed to restore it right prior to executing _WAK, which is after >> > we've executed _BFS. This is a bit theoretical, because no one seems to >> > actaully implement _BFS, but well. >> >> Could we just call _BFS from the "loading" kernel, instead? That would >> save us that copying code... > > I'd prefer not to, because that would require the boot kernel to support ACPI, > which need not (and in fact should not IMO) be the case at present. > > Anyway, we'd have to either copy the NVS data into memory which is mapped and > can be saved, or to map the NVS area in order to save/restore it, which I > wouldn't like to do. io_remap doesn't work at that time? YH