From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751865AbdB0KZY (ORCPT ); Mon, 27 Feb 2017 05:25:24 -0500 Received: from szxga03-in.huawei.com ([45.249.212.189]:3418 "EHLO dggrg03-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751673AbdB0KZU (ORCPT ); Mon, 27 Feb 2017 05:25:20 -0500 Subject: Re: [PATCH RFC] arm64/mm: handle memmap kernel option To: Mark Rutland References: <1488005245-54811-1-git-send-email-xieyisheng1@huawei.com> <20170227084808.GA31271@remoulade> CC: Ard Biesheuvel , Leif Lindholm , Catalin Marinas , "Will Deacon" , Kefeng Wang , Jisheng Zhang , Ganapatrao Kulkarni , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Hanjun Guo , From: Yisheng Xie Message-ID: Date: Mon, 27 Feb 2017 18:24:44 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <20170227084808.GA31271@remoulade> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.29.40] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090206.58B3FE7A.00C7,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 0c9abdb4fdabd2094d47e5a63a24f8c4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org hi Mark, Thanks for comment On 2017/2/27 16:48, Mark Rutland wrote: > Hi, > > On Mon, Feb 27, 2017 at 11:48:50AM +0800, Yisheng Xie wrote: >> On 2017/2/26 18:46, Ard Biesheuvel wrote: >>> On 25 February 2017 at 06:47, Yisheng Xie wrote: > >>>> To make user reserve memory for some specific use more convenient, >>>> this patch implement the following memmap variants: >>>> - memmap=nn[KMG]$ss[KMG]: mark specified memory as reserved; >>>> - memmap=nn[KMG]@ss[KMG]: force usage of a specific region of memory; > >>> Could you explain which problem you are solving here? ACPI implies >>> UEFI on arm64, and so these reservations could be made by a boot >>> component instead, if it requires a fixed memory reservation. If this >>> is a reservation for, e.g., OP-TEE, we should not rely on the command >>> line to communicate this information. >>> >> We just want to reserve some memory for a driver and I just not so familiar >> with how to reserve memory with UEFI. So doubt about whether it is suitable >> to reserve memory with cmdline like "memmap=xxx", which had appeared in x86 >> for a long time. > > Could you please explain for what purpose this is necessary? > > Does the driver need a specific region of memory? Or just some contiguous > region? Or something else? > Yes, we want to use a specific region of memory. > For the former, this is not an appropriate solution; firmware must absolutely > mark the memory as reserved for a particular purpose. > I see, so just forget about this patch. sorry for disturbing. Thanks again for your explain. Yisheng Xie > If you just need contiguous physical memory, I believe it would be better to > use CMA, and request CMA reserve a larger area if necessary. > > Thanks, > Mark. > > . >