From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F300C433EF for ; Wed, 20 Apr 2022 02:13:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348700AbiDTCQ3 (ORCPT ); Tue, 19 Apr 2022 22:16:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229791AbiDTCQ2 (ORCPT ); Tue, 19 Apr 2022 22:16:28 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90B50289BC; Tue, 19 Apr 2022 19:13:43 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Kjkjr0kH9zhXYf; Wed, 20 Apr 2022 10:13:36 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 20 Apr 2022 10:13:41 +0800 Received: from [10.174.178.120] (10.174.178.120) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 20 Apr 2022 10:13:40 +0800 Message-ID: Date: Wed, 20 Apr 2022 10:13:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH v2 0/9] introduce mirrored memory support for arm64 To: CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20220414101314.1250667-1-mawupeng1@huawei.com> <6de859df-e1c3-e9aa-4530-3b61b9c69a28@huawei.com> From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 在 2022/4/20 2:32, Ard Biesheuvel 写道: > On Sat, 16 Apr 2022 at 03:32, mawupeng wrote: >> >> >> >> 在 2022/4/14 18:22, Ard Biesheuvel 写道: >>> On Thu, 14 Apr 2022 at 11:54, Wupeng Ma wrote: >>>> >>>> From: Ma Wupeng >>>> >>>> Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory ranges") >>>> introduced mirrored memory support for x86. This support rely on UEFI to >>>> report mirrored memory address ranges. See UEFI 2.5 spec pages 157-158: >>>> >>>> http://www.uefi.org/sites/default/files/resources/UEFI%202_5.pdf >>>> >>>> Memory mirroring is a technique used to separate memory into two separate >>>> channels, usually on a memory device, like a server. In memory mirroring, >>>> one channel is copied to another to create redundancy. This method makes >>>> input/output (I/O) registers and memory appear with more than one address >>>> range because the same physical byte is accessible at more than one >>>> address. Using memory mirroring, higher memory reliability and a higher >>>> level of memory consolidation are possible. >>>> >>>> Arm64 can support this too. So mirrored memory support is added to support >>>> arm64. >>>> >>>> Efi_fake_mem is used for testing mirrored features and will not be used in >>>> production environment. This test features can fake memory's attribute >>>> values. >>>> >>>> The reason why efi_fake_mem support is put first is that memory's attribute >>>> is reported by BIOS which is hard to simulate. With this support, any arm64 >>>> machines with efi support can easily test mirrored features. >>>> >>>> The main purpose of this patchset is to introduce mirrored support for >>>> arm64 and we have already fixed the problems we had which is shown in >>>> patch #5 to patch #7 and try to bring total isolation in patch #8 which >>>> will disable mirror feature if kernelcore is not specified. >>>> >>>> In order to test this support in arm64: >>>> - patch this patchset >>>> - add efi_fake_mem=8G@0:0x10000 in kernel parameter to simulate mirrored >>>> memroy between phy addr 0-8G. >>>> - add kernelcore=mirror in kernel parameter >>>> - start you kernel >>>> >>> >>> As I explained before: >>> >>> - NAK to EFI fake_mem support on arm64 >> >> fake_mem support on arm64 will be removed in subsequent version. >> >>> - NAK to the whole series until you come up with a proposal on how to >>> locate the static kernel image itself into more reliable memory, as >>> there is really no point to any of this otherwise. >> >> Sorry I am not familiar with this, as you metioned before, >> >> > you have to iterate over the memory map and look for regions with >> > the desired attribute, and allocate those pages explicitly. >> >> Do you mean this is x86, commit c05cd79750fb >> ("x86/boot/KASLR: Prefer mirrored memory regions for the kernel physical address"). >> I will do some research. >> >> > I'd prefer to implement this in the bootloader, and only add minimal >> > logic to the stub to respect the placement of the kernel by the loader >> > if the loader signals it to do so. >> >> Does this bootloader refer to grub and then add minimal logic to arm64-stub.c? >> > > Any bootloader, yes. > >> What is the loader signal? > > A protocol installed onto the image handle, as I suggested before. I > even cc'ed you on a patch that implements this. Sorry to bother you. I didn't receive any patches. Could you share the link? > >> System exists mirrored memory reported by uefi? >> > > What on earth is the point of any of this if the only use case being > targeted is efi_fake_mem with arbitrary fake mirrored regions? > > So yes, unless there are systems that need this, I don't see a point > in merging any of this We do have mirrored memory reported by uefi and efi_fake_mem is added for easy testing with qemu/hardware without update UEFI. > .