From mboxrd@z Thu Jan 1 00:00:00 1970 From: mawupeng Date: Sat, 16 Apr 2022 01:32:01 +0000 Subject: Re: [PATCH v2 0/9] introduce mirrored memory support for arm64 Message-Id: <6de859df-e1c3-e9aa-4530-3b61b9c69a28@huawei.com> List-Id: References: <20220414101314.1250667-1-mawupeng1@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, hpa@zyccr.com, 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 2022/4/14 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? What is the loader signal? System exists mirrored memory reported by uefi? Thanks for reviewing, sorry for my ignorance on this. > .