From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39C394D0CE7; Fri, 9 Oct 2026 16:26:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791563214; cv=none; b=Zp7e1GfOj6x/ebxjTPp/x/O8QhIitEdzqub/XgNFcWds6lHC7zGeGn6TETp5RQ+rKO3JE/C3xPjnRXsQSZIopg/dXA0mff3E4MpRl/KG6ZB4iFfWHCAnpFWETq0IptNoPcn0RdPVY02rnHlnRndoJ8a1xh3dZm9aITZpI82whrM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791563214; c=relaxed/simple; bh=+z9TStifVr8hyP3XMi7kVDq01S8gsy+/HxmSA1n0WxY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jF5cXKZrzoeTe91QOEqSUGNO94wb7HCRcO1jAd5Q694UBUlGgrz+GPoOyMeFMpLgUkWZNGGOwBO9QvDFMMdabLoJWgfcIkZurU6Wkmy/PfHoHyFWPS+np9RD+4AExudUiD/VZzQt95XYg3pc7km6BR7GFhxwvGEzMIYjRIw+IUg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=exb8hAae; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="exb8hAae" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A93D1F000FF; Fri, 9 Oct 2026 16:26:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791563207; bh=P1NQHWvgiocrQrohPdZ3lILWGC/DaP8S52W3+7hraoY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; 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> Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <80af60db-8c39-461c-a488-3dfee990bce8@gmail.com> 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.