From mboxrd@z Thu Jan 1 00:00:00 1970 From: mawupeng Date: Wed, 20 Apr 2022 02:13:40 +0000 Subject: Re: [PATCH v2 0/9] introduce mirrored memory support for arm64 Message-Id: List-Id: References: <20220414101314.1250667-1-mawupeng1@huawei.com> <6de859df-e1c3-e9aa-4530-3b61b9c69a28@huawei.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: ardb@kernel.org Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, dvhart@infradead.org, andy@infradead.org, rppt@kernel.org, paulmck@kernel.org, peterz@infradead.org, jroedel@suse.de, songmuchun@bytedance.com, macro@orcam.me.uk, frederic@kernel.org, W_Armin@gmx.de, john.garry@huawei.com, seanjc@google.com, tsbogend@alpha.franken.de, anshuman.khandual@arm.com, chenhuacai@kernel.org, david@redhat.com, gpiccoli@igalia.com, mark.rutland@arm.com, wangkefeng.wang@huawei.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, linux-ia64@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-mm@kvack.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. > .