From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 20 Jan 2016 14:23:32 +0000 From: Mark Rutland Subject: Re: arm64/efi handling of persistent memory Message-ID: <20160120142330.GA28169@leverpostej> References: <94D0CD8314A33A4D9D801C0FE68B40295BEBD864@G9W0745.americas.hpqcorp.net> <20151218110651.GL25034@bivouac.eciton.net> <20151218114546.GD29219@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ard Biesheuvel Cc: Leif Lindholm , "Elliott, Robert (Persistent Memory)" , "catalin.marinas@arm.com" , "will.deacon@arm.com" , "matt@codeblueprint.co.uk" , "dan.j.williams@intel.com" , "Kani, Toshimitsu" , "Knippers, Linda" , "linux-arm-kernel@lists.infradead.org" , "linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" , Matthew Wilcox , Peter Zijlstra , Theodore Ts'o List-ID: Hi, For those newly Cc'd, the initially reported problem is that arm64 Linux currently treats persistent memory as with any other memory (happily clobbering it), per [1]. On Fri, Dec 18, 2015 at 02:07:10PM +0100, Ard Biesheuvel wrote: > Before we start hacking away at this at the arm64/EFI level, do we > have any documentation and/or consensus regarding how persistent > memory should be treated in the first place? Should it be covered by > memblock? Should it be covered by the linear mapping? Should it be > memblock_reserve()'d? I'm hoping that the lack of replies has more to do with the recent holiday than a lack of opinion... I think that it's sensible to say that at minimum we need to ensure that we don't treat it as available RAM (i.e. we don't clobber it with random data) for now. Per [2] it's not clear to me what the consensus is on memblock, the linear mapping, and the use of struct page, though that's months old so perhaps that's been figured out since. I've Cc'd some of the attendees in case they can clarify the situation. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/394707.html [2] https://lwn.net/Articles/636096/ Thanks, Mark. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933792AbcATOYK (ORCPT ); Wed, 20 Jan 2016 09:24:10 -0500 Received: from foss.arm.com ([217.140.101.70]:45723 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbcATOYI (ORCPT ); Wed, 20 Jan 2016 09:24:08 -0500 Date: Wed, 20 Jan 2016 14:23:32 +0000 From: Mark Rutland To: Ard Biesheuvel Cc: Leif Lindholm , "Elliott, Robert (Persistent Memory)" , "catalin.marinas@arm.com" , "will.deacon@arm.com" , "matt@codeblueprint.co.uk" , "dan.j.williams@intel.com" , "Kani, Toshimitsu" , "Knippers, Linda" , "linux-arm-kernel@lists.infradead.org" , "linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" , Matthew Wilcox , Peter Zijlstra , "Theodore Ts'o" Subject: Re: arm64/efi handling of persistent memory Message-ID: <20160120142330.GA28169@leverpostej> References: <94D0CD8314A33A4D9D801C0FE68B40295BEBD864@G9W0745.americas.hpqcorp.net> <20151218110651.GL25034@bivouac.eciton.net> <20151218114546.GD29219@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, For those newly Cc'd, the initially reported problem is that arm64 Linux currently treats persistent memory as with any other memory (happily clobbering it), per [1]. On Fri, Dec 18, 2015 at 02:07:10PM +0100, Ard Biesheuvel wrote: > Before we start hacking away at this at the arm64/EFI level, do we > have any documentation and/or consensus regarding how persistent > memory should be treated in the first place? Should it be covered by > memblock? Should it be covered by the linear mapping? Should it be > memblock_reserve()'d? I'm hoping that the lack of replies has more to do with the recent holiday than a lack of opinion... I think that it's sensible to say that at minimum we need to ensure that we don't treat it as available RAM (i.e. we don't clobber it with random data) for now. Per [2] it's not clear to me what the consensus is on memblock, the linear mapping, and the use of struct page, though that's months old so perhaps that's been figured out since. I've Cc'd some of the attendees in case they can clarify the situation. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/394707.html [2] https://lwn.net/Articles/636096/ Thanks, Mark. From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Wed, 20 Jan 2016 14:23:32 +0000 Subject: arm64/efi handling of persistent memory In-Reply-To: References: <94D0CD8314A33A4D9D801C0FE68B40295BEBD864@G9W0745.americas.hpqcorp.net> <20151218110651.GL25034@bivouac.eciton.net> <20151218114546.GD29219@leverpostej> Message-ID: <20160120142330.GA28169@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, For those newly Cc'd, the initially reported problem is that arm64 Linux currently treats persistent memory as with any other memory (happily clobbering it), per [1]. On Fri, Dec 18, 2015 at 02:07:10PM +0100, Ard Biesheuvel wrote: > Before we start hacking away at this at the arm64/EFI level, do we > have any documentation and/or consensus regarding how persistent > memory should be treated in the first place? Should it be covered by > memblock? Should it be covered by the linear mapping? Should it be > memblock_reserve()'d? I'm hoping that the lack of replies has more to do with the recent holiday than a lack of opinion... I think that it's sensible to say that at minimum we need to ensure that we don't treat it as available RAM (i.e. we don't clobber it with random data) for now. Per [2] it's not clear to me what the consensus is on memblock, the linear mapping, and the use of struct page, though that's months old so perhaps that's been figured out since. I've Cc'd some of the attendees in case they can clarify the situation. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/394707.html [2] https://lwn.net/Articles/636096/ Thanks, Mark.