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Thu, 03 Sep 2026 07:31:43 +0000 X-Mizu-Trace-ID: 75b7dedc017cd645 X-Migadu-Flow: FLOW_OUT Date: Thu, 3 Sep 2026 15:31:39 +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: <6aef2f48-1cc5-408d-a5a2-2b4b4d45ad7b@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 38891100003 X-Stat-Signature: rge3panb3uokioqcb1be8b5wcw8eskbx X-HE-Tag: 1788420704-684576 X-HE-Meta: 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 Lq/rJgvE DgGf4WqfsqIw9bJMVdyaU4JhMNKGhGaeLNmliWjPpu308iFMnTIz1Rfin5ekrXfwm5WlvnopVuHUbXLKf0kh5CpefC8nJjnBB+m+5rv4BOkVUtq4TABGhc1ptVKGTDbEOImYVjqX8qNIeleK5C/yxcxnUNCOxlL7yEN72CsurHbJAuR268nwtYvT74ZXb3Bw/C0EA0zPmQUm7V3ehY16EjpFmrCQUTcp1JKokoXh3Yy6TaK+0g5Z5lapkX4x7fNjLCid2Ltg4Jm6l3ARdFrz0VNJJqlmYb/ad8DnjmmQvBEDhEh+AUe15H3tD06XFO3O5JTxyqiLDsuOYgNIAyd0XIZWVH6B1XZJHcJi/dL5EO+76MKTWpTb0vpIuLQ== 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 03:05pm, 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? > > 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 > >> >