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([2620:10d:c092:500::5:e213]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab2c964992esm156460966b.185.2025.01.10.03.42.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jan 2025 03:42:09 -0800 (PST) Message-ID: <31ea58e9-147e-4c6d-861e-97f0cc7792bb@gmail.com> Date: Fri, 10 Jan 2025 11:42:08 +0000 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 2/2] efi/memattr: add efi_mem_attr_table as a reserved region in 820_table_firmware To: Dave Young Cc: linux-efi@vger.kernel.org, devel@edk2.groups.io, kexec@lists.infradead.org, ardb@kernel.org, hannes@cmpxchg.org, x86@kernel.org, linux-kernel@vger.kernel.org, leitao@debian.org, gourry@gourry.net, kernel-team@meta.com References: <20250108215957.3437660-1-usamaarif642@gmail.com> <20250108215957.3437660-3-usamaarif642@gmail.com> <4ed67e5b-c2ea-4dc3-b4c5-f8f112b0cd40@gmail.com> Content-Language: en-US From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/01/2025 11:20, Dave Young wrote: > On Fri, 10 Jan 2025 at 19:18, Dave Young wrote: >> >> On Fri, 10 Jan 2025 at 19:12, Usama Arif wrote: >>> >>> >>> >>> On 10/01/2025 02:50, Dave Young wrote: >>>> Hi Usama, >>>> >>>> On Thu, 9 Jan 2025 at 06:00, Usama Arif wrote: >>>>> >>>>> When this area is not reserved, it comes up as usable in >>>>> /sys/firmware/memmap. This means that kexec, which uses that memmap >>>>> to find usable memory regions, can select the region where >>>>> efi_mem_attr_table is and overwrite it and relocate_kernel. >>>> >>>> Is the attr table BOOT SERVICE DATA? If so, does efi_mem_reserve() >>>> work for you? >>>> Just refer to esrt.c. >>>> >>> >>> Hi Dave, >>> >>> Its a bit difficult to reproduce the problem and therefore test the fix, but >>> we are seeing it a lot in production. Ard proposed the same thing in >>> https://lore.kernel.org/all/6b4780a5-ada0-405e-9f0a-4d2186177f29@gmail.com/ >>> but as I mentioned there, I dont think that efi_mem_reserve would help, >>> as efi_mem_reserve changes e820_table, while kexec looks at >>> /sys/firmware/memmap which uses e820_table_firmware. >> >> I sent a question to pm people, if the sysfs memmap comes from >> e820_table then it will be fine. Let's see: > s/e820_table/e820_table_kexec > Do you mean change /sys/firmware/memmap to point to e820_table_kexec instead of e820_table_firmware [1]? I thought of doing this when the first bug was encountered last year, but didn't do it as I thought it would be frowned upon to change what sysfs file exposes to userspace. [1] https://elixir.bootlin.com/linux/v6.12.6/source/arch/x86/kernel/e820.c#L31 >> https://lore.kernel.org/all/CALu+AoS-nk4u=9UYP7BLS=diOxjJRf+vfv7KHXG=uXozoYazsw@mail.gmail.com/ >> >>> >>> Thanks, >>> Usama >>> >>>> Thanks >>>> Dave >>>> >>> >