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Tue, 15 Sep 2026 06:01:20 -0700 (PDT) Message-ID: <13cfcd99-e420-478b-8ce8-06674727977d@gmail.com> Date: Tue, 15 Sep 2026 21:01:07 +0800 Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 00/10] kdump: reduce vmcore size and capture time From: Wandun To: 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, baoquan.he@linux.dev, rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, m.szyprowski@samsung.com Cc: 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> Content-Language: en-US In-Reply-To: <20260902073116.802752-1-chenwandun1@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/2/26 15:31, 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]. > > 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. Hi, Gentle ping on the remaining patches of this series. Patches 1, 7, 8 and 9 have been reviewed (thanks Mike and Marek); Still looking for review on patches 2-6 and 10. Would appreciate a look when you have a moment, happy to rework anything based on feedback. Best regards, Wanun > > 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(-) >