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Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1w4iMe-007fRI-16; Mon, 23 Mar 2026 16:42:50 +0000 Date: Mon, 23 Mar 2026 09:42:38 -0700 From: Breno Leitao To: Jinjie Ruan Cc: corbet@lwn.net, skhan@linuxfoundation.org, catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, kernel@xen0n.name, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, 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, hpa@zytor.com, robh@kernel.org, saravanak@kernel.org, akpm@linux-foundation.org, bhe@redhat.com, vgoyal@redhat.com, dyoung@redhat.com, rdunlap@infradead.org, peterz@infradead.org, feng.tang@linux.alibaba.com, pawan.kumar.gupta@linux.intel.com, dapeng1.mi@linux.intel.com, kees@kernel.org, elver@google.com, paulmck@kernel.org, lirongqing@baidu.com, safinaskar@gmail.com, rppt@kernel.org, ardb@kernel.org, jbohac@suse.cz, cfsworks@gmail.com, osandov@fb.com, tangyouling@kylinos.cn, sourabhjain@linux.ibm.com, ritesh.list@gmail.com, eajames@linux.ibm.com, songshuaishuai@tinylab.org, kevin.brodsky@arm.com, samuel.holland@sifive.com, vishal.moola@gmail.com, junhui.liu@pigmoral.tech, coxu@redhat.com, liaoyuanhong@vivo.com, fuqiang.wang@easystack.cn, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH v9 4/5] arm64: kexec: Add support for crashkernel CMA reservation Message-ID: References: <20260323072745.2481719-1-ruanjinjie@huawei.com> <20260323072745.2481719-5-ruanjinjie@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Debian-User: leitao On Mon, Mar 23, 2026 at 07:17:21PM +0800, Jinjie Ruan wrote: > > > On 2026/3/23 18:20, Breno Leitao wrote: > > On Mon, Mar 23, 2026 at 03:27:44PM +0800, Jinjie Ruan wrote: > >> Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the > >> crashkernel= command line option") and commit ab475510e042 ("kdump: > >> implement reserve_crashkernel_cma") added CMA support for kdump > >> crashkernel reservation. > >> > >> Crash kernel memory reservation wastes production resources if too > >> large, risks kdump failure if too small, and faces allocation difficulties > >> on fragmented systems due to contiguous block constraints. The new > >> CMA-based crashkernel reservation scheme splits the "large fixed > >> reservation" into a "small fixed region + large CMA dynamic region": the > >> CMA memory is available to userspace during normal operation to avoid > >> waste, and is reclaimed for kdump upon crash—saving memory while > >> improving reliability. > >> > >> So extend crashkernel CMA reservation support to arm64. The following > >> changes are made to enable CMA reservation: > >> > >> - Parse and obtain the CMA reservation size along with other crashkernel > >> parameters. > >> - Call reserve_crashkernel_cma() to allocate the CMA region for kdump. > >> - Include the CMA-reserved ranges for kdump kernel to use. > >> - Exclude the CMA-reserved ranges from the crash kernel memory to > >> prevent them from being exported through /proc/vmcore, which is already > >> done in the crash core. > >> > >> Update kernel-parameters.txt to document CMA support for crashkernel on > >> arm64 architecture. > >> > >> Acked-by: Rob Herring (Arm) > >> Acked-by: Baoquan He > >> Acked-by: Mike Rapoport (Microsoft) > >> Acked-by: Ard Biesheuvel > >> Signed-off-by: Jinjie Ruan > >> --- > >> v7: > >> - Correct the inclusion of CMA-reserved ranges for kdump > >> kernel in of/kexec. > >> v3: > >> - Add Acked-by. > >> v2: > >> - Free cmem in prepare_elf_headers() > >> - Add the mtivation. > >> --- > >> Documentation/admin-guide/kernel-parameters.txt | 2 +- > >> arch/arm64/kernel/machine_kexec_file.c | 2 +- > >> arch/arm64/mm/init.c | 5 +++-- > >> drivers/of/fdt.c | 9 +++++---- > >> drivers/of/kexec.c | 9 +++++++++ > >> 5 files changed, 19 insertions(+), 8 deletions(-) > >> > >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > >> index cb850e5290c2..afb3112510f7 100644 > >> --- a/Documentation/admin-guide/kernel-parameters.txt > >> +++ b/Documentation/admin-guide/kernel-parameters.txt > >> @@ -1121,7 +1121,7 @@ Kernel parameters > >> It will be ignored when crashkernel=X,high is not used > >> or memory reserved is below 4G. > >> crashkernel=size[KMG],cma > >> - [KNL, X86, ppc] Reserve additional crash kernel memory from > >> + [KNL, X86, ARM64, PPC] Reserve additional crash kernel memory from > >> CMA. This reservation is usable by the first system's > >> userspace memory and kernel movable allocations (memory > >> balloon, zswap). Pages allocated from this memory range > >> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > >> index c338506a580b..cc577d77df00 100644 > >> --- a/arch/arm64/kernel/machine_kexec_file.c > >> +++ b/arch/arm64/kernel/machine_kexec_file.c > >> @@ -42,7 +42,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image) > >> #ifdef CONFIG_CRASH_DUMP > >> unsigned int arch_get_system_nr_ranges(void) > >> { > >> - unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */ > >> + unsigned int nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */ > > > > You update arch_get_system_nr_ranges() to account for CMA ranges, but > > prepare_elf_headers() in the same file (line 51) still has the > > hardcoded: > > > > nr_ranges = 2; /* for exclusion of crashkernel region */ > > I don't see any logic related to prepare_elf_headers() or hardcoded > nr_ranges = 2 in the arm64 implementation. Just ignore me here, I've mis applied the patch, and then I got arch_get_system_nr_ranges() and prepare_elf_headers(), but, they are the same thing at in here. > > > > and does not exclude CMA ranges from cmem. If the generic crash core > > handles CMA exclusion from vmcore, then shouldn't > > arch_get_system_nr_ranges() also not need this change? > >