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b=nQXXNjLkwYz58zsrBOiKsev3kSoSv0Qn6uiQT1NeTnbVNcw1p5XvMUficJ1jAi+Ak IrQUl6apYNM0BZb+MwY+skimjk4Gaz+DKfu2Z7rrlWqcHeKazOZ/231skNjWs+VoHH hvldwUO3pE+zFitrOfFP0Nw36i/xpINvewLoPaNmIPApssJKO+twQoB8Do6cTfiqc5 iB8xlM34AUVUaxFI7uiDOgQFd78kW0wtR2JuI/FknTclevK64ODgJXoQ+NBv/ZOiVh paTytyIjv85kIpY8OrS5F04vP35/hXTrzck/QL84DN+aQFgoAt0oSjO6j+qJxAzJrr gQoYq19TSfH3Q== Date: Fri, 2 Oct 2026 10:17:05 +0200 From: Mike Rapoport To: Wandun Chen Cc: robh@kernel.org, baoquan.he@linux.dev, m.szyprowski@samsung.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, chenhuacai@kernel.org, kernel@xen0n.name, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, saravanak@kernel.org, akpm@linux-foundation.org, pasha.tatashin@soleen.com, pratyush@kernel.org, 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 v7 0/9] kdump: reduce vmcore size and capture time Message-ID: References: <20260922084256.1515554-1-chenwandun1@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260922084256.1515554-1-chenwandun1@gmail.com> X-Rspamd-Queue-Id: 00C7DC0006 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: w16gaxwjz6qndre4w9nr5b65cqaehs9n X-HE-Tag: 1790929036-496798 X-HE-Meta: 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 9LhH1ZXJ L2D2dxEp5O3ZN27qBaDx0dV/o0SV0yBeM6YqPaZj7lh1hBnXxZQg0pAroebSBvHvu46SOfR9pf17wxl2oiqs8+OL4PfwOhG7CWcMgz2oQnJtQpvV3fZ6MLaTym3Is6WuDdi2O7WpHM1cSXTA5NITI2TUiUKyjJ69uxBgBWilg6W53XPDQjduSvGQwtN9WAPRqumks3NyYgBOeps59FO8osLGF7/G5q1deMrmZiwbAnfEcNKDyhTGc5bk1dmkkp4lHJpIhP32o8CYKcC9Xphp+lVDHQ5/ROWiDQAgsoacUMVEajoSlEKuGxu9qn1mUZbQNaCZAo0Y9T8PY7YmYrxkzzSP3ZU7rDhDB8vfPZX+qYdOu36jHHu5BmFoaexNV9g11W7FhyqreeFrknzo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Wandun, On Tue, Sep 22, 2026 at 04:42:47PM +0800, 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 are marked MEMBLOCK_NODUMP by default 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 both ACPI and DT systems > can benefit from it (suggested by Rob, thanks). Can you elaborate how ACPI systems filter their reserved memory? With your patches, the memblock flag becomes a part of DT-only infrastructure, so that claim that both ACPI and DT benefit from it does not hold, doesn't it? > 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 1-3: Preparation and bugfixes: 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 4-8: 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 9: Exclude MEMBLOCK_NODUMP regions from the vmcore ELF > header. > > v6 --> v7: > 1. Fix a stale MEMBLOCK_NODUMP flag issue [1]. Memory reserved and > marked as NODUMP may later be freed (the initrd, for example), > so the NODUMP flag must be cleared accordingly. Since the fix is > part of the NODUMP infrastructure introduced by patch 5, it has > been folded into that patch. > > 2. Drop the "generic" related description in the cover letter. > > 3. Collect the Acked-by and Reviewed-by tags received during the v6 > review (thanks to Baoquan, Mike, Rob and Marek). Patch 5 is the > only one without a tag, as its Reviewed-by was dropped when the > fix was folded in. > > 4. Drop patch 1 of v6, which has been merged separately. > > > 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]. > 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://sashiko.dev/#/message/20260917220750.GA4013814-robh%40kernel.org > [2] https://lore.kernel.org/lkml/20260723234126.GA3253409-robh@kernel.org/ > [3] https://lore.kernel.org/lkml/20260506144542.GA2072596-robh@kernel.org/ > > > > 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 | 43 +++++++++++++++++- > 14 files changed, 155 insertions(+), 97 deletions(-) > > -- > 2.43.0 > -- Sincerely yours, Mike.