From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752735AbaBVWaX (ORCPT ); Sat, 22 Feb 2014 17:30:23 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:38038 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752159AbaBVWaV (ORCPT ); Sat, 22 Feb 2014 17:30:21 -0500 Date: Sat, 22 Feb 2014 23:30:19 +0100 From: Pavel Machek To: Russell King - ARM Linux Cc: Lorenzo Pieralisi , Sebastian Capella , "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "linaro-kernel@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , Russ Dill , "Rafael J. Wysocki" , Len Brown , Nicolas Pitre , Santosh Shilimkar , Will Deacon , Cyril Chemparathy , Jonathan Austin , Catalin Marinas , Uwe Kleine-K?nig , Stephen Boyd Subject: Re: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk Message-ID: <20140222223019.GB20490@amd.pavel.ucw.cz> References: <1392774729-3235-1-git-send-email-sebastian.capella@linaro.org> <1392774729-3235-4-git-send-email-sebastian.capella@linaro.org> <20140219161254.GB19343@e102568-lin.cambridge.arm.com> <20140219193315.3732.21819@capellas-linux> <20140220162754.GC15994@e102568-lin.cambridge.arm.com> <20140222101655.GE21483@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140222101655.GE21483@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 2014-02-22 10:16:55, Russell King - ARM Linux wrote: > On Thu, Feb 20, 2014 at 04:27:55PM +0000, Lorenzo Pieralisi wrote: > > I still do not understand why switching to idmap, which is a clone of > > init_mm + 1:1 kernel mappings is required here. Why idmap ? > > > > And while at it, can't the idmap be overwritten _while_ copying back the > > resume kernel ? Is it safe to use idmap page tables while copying ? > > > > I had a look at x86 and there idmap page tables used to resume are created > > on the fly using safe pages, on ARM idmap is created at boot. > > That's fine. > > Remember, you're required to boot exactly the same kernel image when > resuming as the kernel which created the suspend image. Unless you > have random allocations going on, you should get the same layout for > the idmap stuff at each boot. Actually, x86-64 is able to resume from different kernel these days, and some day you may want to do it on arm, too. But it is definitely not needed for inital merge. Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk Date: Sat, 22 Feb 2014 23:30:19 +0100 Message-ID: <20140222223019.GB20490@amd.pavel.ucw.cz> References: <1392774729-3235-1-git-send-email-sebastian.capella@linaro.org> <1392774729-3235-4-git-send-email-sebastian.capella@linaro.org> <20140219161254.GB19343@e102568-lin.cambridge.arm.com> <20140219193315.3732.21819@capellas-linux> <20140220162754.GC15994@e102568-lin.cambridge.arm.com> <20140222101655.GE21483@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:38038 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752159AbaBVWaV (ORCPT ); Sat, 22 Feb 2014 17:30:21 -0500 Content-Disposition: inline In-Reply-To: <20140222101655.GE21483@n2100.arm.linux.org.uk> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Russell King - ARM Linux Cc: Lorenzo Pieralisi , Sebastian Capella , "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "linaro-kernel@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , Russ Dill , "Rafael J. Wysocki" , Len Brown , Nicolas Pitre , Santosh Shilimkar , Will Deacon , Cyril Chemparathy , Jonathan Austin , Catalin Marinas , Uwe Kleine-K?nig , Stephen Boyd On Sat 2014-02-22 10:16:55, Russell King - ARM Linux wrote: > On Thu, Feb 20, 2014 at 04:27:55PM +0000, Lorenzo Pieralisi wrote: > > I still do not understand why switching to idmap, which is a clone of > > init_mm + 1:1 kernel mappings is required here. Why idmap ? > > > > And while at it, can't the idmap be overwritten _while_ copying back the > > resume kernel ? Is it safe to use idmap page tables while copying ? > > > > I had a look at x86 and there idmap page tables used to resume are created > > on the fly using safe pages, on ARM idmap is created at boot. > > That's fine. > > Remember, you're required to boot exactly the same kernel image when > resuming as the kernel which created the suspend image. Unless you > have random allocations going on, you should get the same layout for > the idmap stuff at each boot. Actually, x86-64 is able to resume from different kernel these days, and some day you may want to do it on arm, too. But it is definitely not needed for inital merge. Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: pavel@ucw.cz (Pavel Machek) Date: Sat, 22 Feb 2014 23:30:19 +0100 Subject: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk In-Reply-To: <20140222101655.GE21483@n2100.arm.linux.org.uk> References: <1392774729-3235-1-git-send-email-sebastian.capella@linaro.org> <1392774729-3235-4-git-send-email-sebastian.capella@linaro.org> <20140219161254.GB19343@e102568-lin.cambridge.arm.com> <20140219193315.3732.21819@capellas-linux> <20140220162754.GC15994@e102568-lin.cambridge.arm.com> <20140222101655.GE21483@n2100.arm.linux.org.uk> Message-ID: <20140222223019.GB20490@amd.pavel.ucw.cz> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat 2014-02-22 10:16:55, Russell King - ARM Linux wrote: > On Thu, Feb 20, 2014 at 04:27:55PM +0000, Lorenzo Pieralisi wrote: > > I still do not understand why switching to idmap, which is a clone of > > init_mm + 1:1 kernel mappings is required here. Why idmap ? > > > > And while at it, can't the idmap be overwritten _while_ copying back the > > resume kernel ? Is it safe to use idmap page tables while copying ? > > > > I had a look at x86 and there idmap page tables used to resume are created > > on the fly using safe pages, on ARM idmap is created at boot. > > That's fine. > > Remember, you're required to boot exactly the same kernel image when > resuming as the kernel which created the suspend image. Unless you > have random allocations going on, you should get the same layout for > the idmap stuff at each boot. Actually, x86-64 is able to resume from different kernel these days, and some day you may want to do it on arm, too. But it is definitely not needed for inital merge. Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html