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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xFE73-00000006lYY-2bUD; Fri, 09 Oct 2026 17:10:29 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xFE72-00000006lY7-2T3J; Fri, 09 Oct 2026 17:10:28 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id E468243F04; Fri, 9 Oct 2026 17:10:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86F951F000FF; Fri, 9 Oct 2026 17:10:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791565827; bh=kAD7jZL3WT2oDggDD/W1Uk0YnF3NERQV17t5J8hJ8+M=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Q1Nhseaoa+rDmPgv3RV88Xq/keczcbIu4FLYepJnBvD2cRWQ9lipkpUB7/oP4GWM2 FtecI4n/MNfujCQ2qyTF3wHtE8IruMwItFTLmIBKKeC3vlmY0G1hsyyVZAtoiwWou8 P3DbUqJp9Xmpt/k5D8+TZwqQdKWqiN19Lf+AJ3W0+6UWmvY9NsCpCPQCR2qUhmOLIC 8Ojr7flTBUGp+qSaJwC9QVMRhzWedJSGwa8czVneuywDeGOD4MwdC3oFvmjdVrC/MQ pQQu6ro5HclX1M3k8qO/i9gCSAbnfYwfDkfc5jGddIzvabPGzItOqeLhZ1tE9Uequ/ TaRWxOs50oK2g== Date: Fri, 9 Oct 2026 12:10:27 -0500 From: Rob Herring To: Mike Rapoport Cc: Wandun , 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: <20261009171027.GA2734758-robh@kernel.org> 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: X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Oct 09, 2026 at 06:26:36PM +0200, Mike Rapoport wrote: > 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? IIUC, NOMAP implies NODUMP (for EFI and DT), but NODUMP is needed for some mapped (!NOMAP) regions. Rob