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b=exb8hAaeBUkFUrpnnUkhqLQ5zgFgMWnN/rYINMuBzDs1GNM4i9JO2MPVFhuXRhFo0 bqz3igmYBv7ZBuRWS/kvuYQ5ffUaHTPuDsrkHE/UxTZ8gJOgIGsoInf5FsQ/UB7y3A g6CVRHuOO5bxRC/opNlTJ4l+8W+7F8avwelRbJO07mkTvjpRefiI3V10A1GVbXs3Go XiKBGRBT0rS5eYl1YAt1D6JtcC8KFP/8pAvYu+y+q/bNxjXRUhITPA1EQMMGGJt/eI lisapvQarlC5G9y4IP9ryxp+vI8vfLGLmBHwRi5eyGkWEwhSa/zfu2VmAVl2fAr/CB DWas7S1aHp1/A== Date: Fri, 9 Oct 2026 18:26:36 +0200 From: Mike Rapoport To: Wandun 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> <80af60db-8c39-461c-a488-3dfee990bce8@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <80af60db-8c39-461c-a488-3dfee990bce8@gmail.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2FC41180007 X-Rspam-User: X-Stat-Signature: yfgy465fzmh3nahxd7f5o4x7d9obhaoh X-HE-Tag: 1791563209-141480 X-HE-Meta: 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 WoOmezYk 6cn6AFVrXBOA7Alhk/kVSuKQyTjkgg5am+66X3lmrWka2YYzciO84yviRgBRhDfcJ7n6HG+rgO5xLlnsBbKu6DkxUSa5nPSSBnjfmsB3SqZKwxTZRlWiF8uBXiAVuZ9mzoBDekAn4qsRl35FBQdE9Kt3SDwBRNbxnUffxqwr8strI0eS7r8Av5Gzchj2s7Fbf2m67X+AlWTE7t7JUEGkJi18DS6FRLgODxQnUeJGWTYG2pOHg+h+LFFWsVUORW4p6/5abzvqu0GBZTf86YcWjulopR7Bm84OUsya6NJLf5Jt+l/7/B5HXz2ssSjHxNEdAzGmkJ4xTTXtfT0QhiEjgzibuz9iC2abzFUb2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 09, 2026 at 11:04:47AM +0800, Wandun wrote: > On 10/2/26 16:17, Mike Rapoport wrote: > > 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). > > > Hi Mike, > > Thanks for the review. > > > Can you elaborate how ACPI systems filter their reserved memory? > > In the EFI memory map, firmware carveouts are reported with the type > EFI_RESERVED_TYPE. This type of memory gets the nomap flag set in > memblock.memory (is_usable_memory() returns false in reserve_regions() > and mark these regions with nomap flag), during prepare_elf_headers(), > for_each_mem_range() filters out these nomap regions. Therefore, the > memory reserved on ACPI based systems will not be dumped into the vmcore. > > I will add these description in next version. > > > 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? > > You are right, the wording was misleading. Let me clarify what I meant. > > In this series only DT marks regions as MEMBLOCK_NODUMP: > /reserved-memory and /memreserve/ entries are tagged in the OF > paths (of_reserved_mem.c, fdt.c). ACPI does not set the flag and > keeps filtering its reserved memory through the existing path, as > described above. > > > What I intended to convey is that the flag itself lives in memblock > rather than on the DT-only struct reserved_mem, so it is available > for reuse. If an ACPI system ever needed to exclude a firmware-owned > region from the vmcore, it could mark that region with MEMBLOCK_NODUMP > the same way DT does, instead of having to invent a parallel mechanism. > That is a future option, not something this series enables for ACPI > today. So, EFI uses NOMAP for the same purpose, right? Why when we need a new memblock flag then? > Also will update these description in next verison. > > Best regards, > Wandun -- Sincerely yours, Mike.