From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BDD27C61DD3 for ; Thu, 3 Sep 2026 09:38:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=1MZQdmy+aD6EzeJNs6e/eUAQKmqctsgijH/5ayyWVio=; b=T/ccyycqhTh+1cA6QiwELTBSZd 42VBUhq2riTk0P4DaBaNZRV5U9PR3e6SWCYiMy5zlXAJSGd/yUzczRs6Vg8JkBSfsBLjxQPVz5HXx 9cdWW+gZtLF0f115eYQvG35tWD7XqL615xWEnKHHWyNm5B4SlNIu9en+2RxKmofzSkZdZnHW5tv0k FKephaIS06g6vtUEXu66J+sgvDvmvZFXIkUOMqlBrTN13XVDN1thrpIgYgXsywKj1JOPRcL3zU+TA tF3v3EAAgJueXXHpZqoe9PmcYhK3L9xxQwvMMrFVcrIvKk8cstS/bAhC4qJUbDiD3jJdI6nPH1yKz PKzL0ing==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x23tl-0000000GySt-3xUb; Thu, 03 Sep 2026 09:38:21 +0000 Received: from out-37.mta1.migadu.com ([95.215.58.37] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x23ti-0000000GyRb-0ucc for kexec@lists.infradead.org; Thu, 03 Sep 2026 09:38:19 +0000 X-Envelope-To: kexec@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=xkq56dwf8DBNdrzi3qeWturDMdOajTLtoV/DhFx+x38=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788428296; v=1; x=1789033096; b=dJKMYrpSu9hn6T+tGDlWJlDQ8ca+hlEszTRs1d1hxr5tWLbMftClkEyJ+BrqB5HWh5zDTwEj +M1lOPYdCmPeU1VkaX/CkgZxJpZiXRV30o9RlQMJnKHfHhc3BBU2gUfa7h6YXs/1FpWFbE4Xd9X IVSYZ1HJ3fRjiN7HazC+Ob3Y= X-Envelope-To: kexec@lists.infradead.org Received: by mta10.migadu.com with ESMTPS id 4c96c0b4fdde9bc3; Thu, 03 Sep 2026 09:38:16 +0000 X-Mizu-Trace-ID: 4c96c0b4fdde9bc3 X-Migadu-Flow: FLOW_OUT Date: Thu, 3 Sep 2026 17:38:11 +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: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260903_023818_405168_12F044DE X-CRM114-Status: GOOD ( 38.47 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 09/03/26 at 03:43pm, Wandun wrote: > > > On 9/3/26 15:31, Baoquan He wrote: > > 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? > > Yes, still good, only need to pass the physical range to memblock_mark_nodump(). That's interesting. If drivers or any component allocate memory from buddy, then you will call memblock_mark_nodump() to mark the region specifically (memblock_setclr_flag will split regions if it's a sub region of existing memblock region), it won't impact anything? > > > > >> > >> 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 > >>>> > >> >