From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752798AbaBVKRL (ORCPT ); Sat, 22 Feb 2014 05:17:11 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:46749 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752322AbaBVKRI (ORCPT ); Sat, 22 Feb 2014 05:17:08 -0500 Date: Sat, 22 Feb 2014 10:16:55 +0000 From: Russell King - ARM Linux To: Lorenzo Pieralisi Cc: 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 , Pavel Machek , 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: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140220162754.GC15994@e102568-lin.cambridge.arm.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk Date: Sat, 22 Feb 2014 10:16:55 +0000 Message-ID: <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:46750 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752389AbaBVKRK (ORCPT ); Sat, 22 Feb 2014 05:17:10 -0500 Content-Disposition: inline In-Reply-To: <20140220162754.GC15994@e102568-lin.cambridge.arm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Lorenzo Pieralisi Cc: 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 , Pavel Machek , Nicolas Pitre , Santosh Shilimkar , Will Deacon , Cyril Chemparathy , Jonathan Austin , Catalin Marinas , Uwe Kleine-K?nig , Stephen Boyd 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. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Sat, 22 Feb 2014 10:16:55 +0000 Subject: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk In-Reply-To: <20140220162754.GC15994@e102568-lin.cambridge.arm.com> 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> Message-ID: <20140222101655.GE21483@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit".