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Tue, 27 Jan 2026 17:46:13 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: AI0CEnD8AI8k Date: Tue, 27 Jan 2026 23:45:53 +0100 From: "Ard Biesheuvel" To: "Jinjie Ruan" , leitao@debian.org, corbet@lwn.net, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, bp@alien8.de, mingo@kernel.org, pawan.kumar.gupta@linux.intel.com, feng.tang@linux.alibaba.com, "Kees Cook" , elver@google.com, arnd@arndb.de, fvdl@google.com, lirongqing@baidu.com, bhelgaas@google.com, bhe@redhat.com, dave.hansen@linux.intel.com, rppt@kernel.org, cfsworks@gmail.com, osandov@fb.com, sourabhjain@linux.ibm.com, jbohac@suse.cz, "Ryan Roberts" , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Message-Id: In-Reply-To: <20260126081334.699147-1-ruanjinjie@huawei.com> References: <20260126081334.699147-1-ruanjinjie@huawei.com> Subject: Re: [PATCH v2] arm64: kexec: Add support for crashkernel CMA reservation Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Mon, 26 Jan 2026, at 09:13, Jinjie Ruan wrote: > Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the > crashkernel=3D 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 difficul= ties > 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": t= he > CMA memory is available to userspace during normal operation to avoid > waste, and is reclaimed for kdump upon crash=E2=80=94saving memory whi= le > 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 crashkern= el > 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. > > Update kernel-parameters.txt to document CMA support for crashkernel on > arm64 architecture. > > Signed-off-by: Jinjie Ruan > --- > v2: > - Free cmem in prepare_elf_headers() > - Add the mtivation. > --- > Documentation/admin-guide/kernel-parameters.txt | 2 +- > arch/arm64/kernel/machine_kexec_file.c | 15 ++++++++++++++- > arch/arm64/mm/init.c | 5 +++-- > 3 files changed, 18 insertions(+), 4 deletions(-) > Thanks for respinning the commit log. I am not an expert but this looks reasonable to me, so Acked-by: Ard Biesheuvel > diff --git a/Documentation/admin-guide/kernel-parameters.txt=20 > b/Documentation/admin-guide/kernel-parameters.txt > index 1058f2a6d6a8..36bb642a7edd 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1119,7 +1119,7 @@ Kernel parameters > It will be ignored when crashkernel=3DX,high is not used > or memory reserved is below 4G. > crashkernel=3Dsize[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=20 > b/arch/arm64/kernel/machine_kexec_file.c > index 410060ebd86d..ef6ce9aaba80 100644 > --- a/arch/arm64/kernel/machine_kexec_file.c > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -48,7 +48,7 @@ static int prepare_elf_headers(void **addr, unsigned=20 > long *sz) > u64 i; > phys_addr_t start, end; >=20 > - nr_ranges =3D 2; /* for exclusion of crashkernel region */ > + nr_ranges =3D 2 + crashk_cma_cnt; /* for exclusion of crashkernel re= gion */ > for_each_mem_range(i, &start, &end) > nr_ranges++; >=20 > @@ -64,6 +64,12 @@ static int prepare_elf_headers(void **addr, unsigne= d=20 > long *sz) > cmem->nr_ranges++; > } >=20 > + for (i =3D 0; i < crashk_cma_cnt; i++) { > + cmem->ranges[cmem->nr_ranges].start =3D crashk_cma_ranges[i].start; > + cmem->ranges[cmem->nr_ranges].end =3D crashk_cma_ranges[i].end; > + cmem->nr_ranges++; > + } > + > /* Exclude crashkernel region */ > ret =3D crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.e= nd); > if (ret) > @@ -75,6 +81,13 @@ static int prepare_elf_headers(void **addr, unsigne= d=20 > long *sz) > goto out; > } >=20 > + for (i =3D 0; i < crashk_cma_cnt; ++i) { > + ret =3D crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start, > + crashk_cma_ranges[i].end); > + if (ret) > + goto out; > + } > + > ret =3D crash_prepare_elf64_headers(cmem, true, addr, sz); >=20 > out: > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 524d34a0e921..28165d94af08 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -96,8 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit; >=20 > static void __init arch_reserve_crashkernel(void) > { > + unsigned long long crash_base, crash_size, cma_size =3D 0; > unsigned long long low_size =3D 0; > - unsigned long long crash_base, crash_size; > bool high =3D false; > int ret; >=20 > @@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void) >=20 > ret =3D parse_crashkernel(boot_command_line, memblock_phys_mem_size(= ), > &crash_size, &crash_base, > - &low_size, NULL, &high); > + &low_size, &cma_size, &high); > if (ret) > return; >=20 > reserve_crashkernel_generic(crash_size, crash_base, low_size, high); > + reserve_crashkernel_cma(cma_size); > } >=20 > static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit) > --=20 > 2.34.1