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Thu, 03 Sep 2026 09:38:16 +0000 X-Mizu-Trace-ID: 4c96c0b4fdde9bc3 X-Migadu-Flow: FLOW_OUT Date: Thu, 3 Sep 2026 17:38:11 +0800 From: Baoquan He To: Wandun 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 Subject: Re: [PATCH v6 00/10] kdump: reduce vmcore size and capture time Message-ID: References: <20260902073116.802752-1-chenwandun1@gmail.com> <6aef2f48-1cc5-408d-a5a2-2b4b4d45ad7b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: gmzgz719fp8j83xxftbaujasqydcf95e X-Rspamd-Queue-Id: 640AB20004 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788428309-414020 X-HE-Meta: U2FsdGVkX18uVKWR/qSRNQBF5Cwi1+exqaL84feRwZDFQzhEZ5hmT6sqU2/iSE031x+ERQjK18E8r0I+DWqNZoqSRwVZS0dpJgIPTLsSRSl2y+j3WsVlcYnHny9h/TU//LgLL7PBNw/ehPtn4ouwLoG4LdNOcJNYHQ82nVtzgQUo2NobvASYoFsAuxXKvat9onuN1KRUOL+sHazojP+oAHRWsGnBRoW0VNnDvkQNp8FoCtVzF3S8LUgF4e2b47nHpiMFDlNzX83r/QOXfkUF7NMms5KjgGkG+EJNIfLXjeSxxS0TVOyMNOoob8npwjOXJ9B1CFdvXXG63wCnHT7O07nDS22D4pKCcs2LpGkwU/Yy/L7dBqQbVOjtKy1npow2tgqbZRX0qFAPenUYTcybPGO8Jh5X8sAIUaLGnVTVoZpKppyI9AMxbH1fFt15eZqHQq/4Ijr8Jpa1gc19xPcDTNGCe08LW57TAMUIVOKbpbFtvHV66tytsX1kmIpUDRY2F8iq8WUr/nUmQoLck4mJSBNUPbnSYIyLpZ7X6UO+TW2ySjpz1ufmckdx0lrsfJMcmhrw4V6spI+UI6I1PiJH2VtzUGELa0tKoNv+pO2JAw4QQ64wR7IF0B2RCQBgOhtnU9gt+MVDKP73onHwghr0gFez8J/OKZG0NkIKixDbH63E5gNexP0i+SZVELcU916RKaSrJc9KjWDPQa7CwLRgGqFo0JqhvmPpjRbP6pN96aR3XckdAzGF8yKVUodLjADa0izZaut5pkKZUDDjMm29798PTP8SOv3xeGjArJ8c8ShXixpVK/Oyi56rl/SBAx7BrXUtowPzr75Ms8WPom4buYJfw2DwxqlxKb0IPSR0vA/l0aXtPcX1awhfbC6jobVqAYUBRxnlMvxYdceHq06/A8/bPEYLW6yoIL2yk6f1zqpVQ0ys48zgVe/mi2OrkeImpYBKpKD84gWB71/kXts sCeUWnEz hfdE4Ab8gup3Xou9/Xrl2Pi60WkVg6eUg9qhPEZzN/mUklRvebHPT2+qb4NtafY9wPoGPcU/cDSq1zTXJYXyHSO1+ChynIyFJy08D58j1QAGhx8/63uHJd3kulJ8eKnKh8I8ScUGYvTCHiLzhhKRrPB0musv1VGydFdIJ5nDqrRbeOeJaLUu1JpMYHhrrsj/0EMDy/CyzloPf4saNaoNu9LQcsQF2IoFHlLyoOymKCH1MvzGI0ZQGej/2aOILF9ev78JOWfqsE2Zi0CzXMBAbljHm8hFba5H45D4txVX11mtYs1cOLTnBp6YuO3sqq/0VTomZ5fhuZbLgocrmX7XREoOm7ZFArQMwtI8e+cTDjgOI+BQMNYtsKO8sxQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/03/26 at 03:43pm, Wandun wrote: > > > 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(). That's interesting. If drivers or any component allocate memory from buddy, then you will call memblock_mark_nodump() to mark the region specifically (memblock_setclr_flag will split regions if it's a sub region of existing memblock region), it won't impact anything? > > > > >> > >> 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 > >>>> > >> >