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Thu, 03 Sep 2026 00:44:11 -0700 (PDT) Received: from [10.125.112.20] ([122.11.210.25]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2dafe62d7c2sm5931425ad.29.2026.09.03.00.44.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Sep 2026 00:44:11 -0700 (PDT) Message-ID: Date: Thu, 3 Sep 2026 15:43:58 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 00/10] kdump: reduce vmcore size and capture time To: Baoquan He Cc: catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, robh@kernel.org, saravanak@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, m.szyprowski@samsung.com, mark.rutland@arm.com, kernel@xen0n.name, alex@ghiti.fr, hpa@zytor.com, ruirui.yang@linux.dev, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, iommu@lists.linux.dev References: <20260902073116.802752-1-chenwandun1@gmail.com> <6aef2f48-1cc5-408d-a5a2-2b4b4d45ad7b@gmail.com> Content-Language: en-US From: Wandun In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260903_004413_508293_D9AB5A64 X-CRM114-Status: GOOD ( 25.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/3/26 15:31, Baoquan He wrote: > On 09/03/26 at 03:05pm, Wandun wrote: >> >> >> On 9/2/26 16:53, Baoquan He wrote: >>> Hi Wandun, >>> >>> On 09/02/26 at 03:31pm, Wandun Chen wrote: >>>> From: Wandun Chen >>>> >>>> On SoCs that carve out large firmware-owned reserved memory (GPU, >>>> camera ISP, ...), kdump currently dumps those carveouts as part of >>>> system RAM even though their contents are firmware state that is not >>>> useful for kernel crash analysis. >>>> >>>> This series introduces a MEMBLOCK_NODUMP flag in memblock to filter >>>> reserved memory on DT-based architectures (arm64, riscv, loongarch). >>>> Reserved regions default are marked MEMBLOCK_NODUMP so kdump omits them; >>>> reusable CMA regions are different because their pages are handed back >>>> to the buddy allocator and may carry crash-relevant data. >>>> >>>> ACPI systems already filter reserved memory out of the vmcore through >>>> their existing path; only DT-based systems currently fail to filter these >>>> regions, which is what this series addresses. The flag lives in memblock >>>> itself rather than in a DT-only structure, so the mechanism is generic and >>>> both ACPI and DT systems can benefit from it (suggested by Rob, thanks) [1]. >>> >>> Thanks for the effort. I am not against this patchset, and I haven't >>> went through it carefully. Just from the cover letter, you mentioned >>> generic, I am wondering if this can be generic for excluding other >>> memory regions. Asking this because I try to find a way to exclude >>> unwanted memory regions too, please check below link where there's >>> the relevant discussion. We definitely don't like inventing wheels >>> time after time. Do you think this memblock region excluding can >>> be used in other places of kernel? >>> >>> https://lore.kernel.org/all/aoLFai0gzzH2bGgy@MiWiFi-R3L-srv/T/#u >> >> >> Thanks for taking a look, and for the pointer to the crash-wipe thread. >> >> To answer your question directly: the exclusion mechanism in this series >> is already generic, memblock_mark_nodump() is the entry point. Any code >> that wants a region out of the vmcore just marks it MEMBLOCK_NODUMP, when >> preparing vmcore elf header by walking memblock, these regionss are skipped; >> This series is simply one caller, marking the DTS /reserved-memory and >> /memreserve/ regions with MEMBLOCK_NODUMP. > > Thanks, for memory not allocated from memblock, e.g buddy, is it still > good? Yes, still good, only need to pass the physical range to memblock_mark_nodump(). > >> >> x86 currently builds the vmcore elf header from iomem_resource, not >> memblock; it could be switched to memblock, but that would bring no >> benefit for the problem this series solves, so this series makes no >> x86 change. I'd personally be in favor of switching to memblock for >> a unified implementation across architectures. >> >> Best regards >> Wandun >> >> >>> >>>> >>>> Since the reserved memory regions are filtered out, the vmcore is >>>> smaller in size and faster to produce. >>>> >>>> The series is based on linux-next and is organized as follows: >>>> >>>> Patches 1-4: Preparation and bugfixes: fix the missing HugeTLB >>>> flagname, switch riscv crash_mem to memblock, fold the >>>> duplicated per-arch memblock walks into the weak >>>> defaults, and serialize crash header preparation against >>>> memory hotplug. >>>> Patches 5-9: NODUMP infrastructure: switch crash_core to >>>> for_each_mem_region(), introduce the MEMBLOCK_NODUMP >>>> flag, add a dumpable flag to struct reserved_mem, and >>>> mark /reserved-memory and /memreserve/ entries with >>>> MEMBLOCK_NODUMP flag. >>>> Patch 10: Exclude MEMBLOCK_NODUMP regions from the vmcore ELF >>>> header. >>>> >>>> In v5, Sashiko found some pre-existing issues related to reserved-memory, >>>> and has no dependency on this series, so these issues have been addressed >>>> in a separate series [2]. >>>> >>>> v5 --> v6: >>>> 1. Serialize crash header preparation against memory hotplug to avoid >>>> out-of-bounds or use-after-free issues. >>>> >>>> 2. MEMBLOCK_NODUMP marking is now done after memblock allows resizing, >>>> avoiding a panic from too few regions before resize is permitted. >>>> >>>> 3. Reordered the patches, put pre-existing bugfixes earlier in the series. >>>> >>>> >>>> v4 --> v5: >>>> 1. Rework the mechanism around a memblock-level MEMBLOCK_NODUMP flag >>>> (suggested by Rob) instead of the v4 opt-in 'dumpable' flag on >>>> DT-only struct reserved_mem. >>>> 2. Switch the riscv vmcore elf header preparation to use memblock >>>> instead of the resource tree, aligning it with arm64 and loongarch, >>>> so riscv also can exclude reserved memory from vmcore. >>>> 3. Deduplicate the vmcore elf header preparation: arm64, riscv and >>>> loongarch open-coded the same logic, so fold it into shared >>>> __weak defaults in crash_core. >>>> 4. Drop the v4 patch that saved /memreserve/ entries into the >>>> reserved_mem array; /memreserve/ is now marked MEMBLOCK_NODUMP >>>> directly. >>>> >>>> v3 --> v4: >>>> 1. Rebase this series on v7.2-rc1. >>>> 2. Add two cleanup patches (patch 02/03). >>>> 3. Simplify patch 03 to avoid checking whether initial_boot_params is >>>> NULL multiple times, suggested by Rob. >>>> >>>> v2 --> v3: >>>> 1. Fix out-of-bounds issue if device tree lacks /reserved-memory node. >>>> 2. Fix UAF issue when alloc_reserved_mem_array() fails. >>>> 3. Add some prepare patches. >>>> >>>> v1 --> v2: >>>> 1. v1 added an opt-out DT property ('linux,no-dump'). Per Rob's >>>> feedback [3], v2 drop that property and exclude reserve memory >>>> by default. >>>> 2. Split some prepared patches from the original patches. >>>> 3. Address coding-style comments on patch 5 from Rob. >>>> >>>> [1] https://lore.kernel.org/lkml/20260723234126.GA3253409-robh@kernel.org/ >>>> [2] https://lore.kernel.org/lkml/20260818092420.2859026-1-chenwandun1@gmail.com/ >>>> [3] https://lore.kernel.org/lkml/20260506144542.GA2072596-robh@kernel.org/ >>>> >>>> Meijing Zhao (1): >>>> mm: memblock: add missing HugeTLB flag name >>>> >>>> Wandun Chen (9): >>>> riscv: build crash_mem ranges from memblock instead of resource tree >>>> crash_core: fold duplicated memblock arch hooks into the weak default >>>> crash_core: serialize crash header preparation against hotplug >>>> crash_core: replace for_each_mem_range() with for_each_mem_region() >>>> memblock: introduce MEMBLOCK_NODUMP flag >>>> of: reserved_mem: add dumpable flag to opt-in vmcore >>>> of: reserved_mem: mark /reserved-memory entries with MEMBLOCK_NODUMP >>>> of: reserved_mem: mark /memreserve/ entries as MEMBLOCK_NODUMP >>>> crash_core: skip MEMBLOCK_NODUMP regions when building vmcore ELF >>>> header >>>> >>>> arch/arm64/kernel/machine_kexec_file.c | 29 ------------ >>>> arch/loongarch/kernel/machine_kexec_file.c | 27 ------------ >>>> arch/riscv/Kconfig | 2 +- >>>> arch/riscv/kernel/machine_kexec_file.c | 33 -------------- >>>> arch/x86/kernel/crash.c | 2 +- >>>> drivers/of/fdt.c | 2 + >>>> drivers/of/of_private.h | 2 + >>>> drivers/of/of_reserved_mem.c | 48 ++++++++++++++++++++ >>>> include/linux/crash_core.h | 2 + >>>> include/linux/memblock.h | 9 ++++ >>>> include/linux/of_reserved_mem.h | 1 + >>>> kernel/crash_core.c | 51 ++++++++++++++++++++-- >>>> kernel/dma/contiguous.c | 1 + >>>> mm/memblock.c | 17 ++++++++ >>>> 14 files changed, 131 insertions(+), 95 deletions(-) >>>> >>>> -- >>>> 2.43.0 >>>> >>