From: Breno Leitao <leitao@debian•org>
To: Jinjie Ruan <ruanjinjie@huawei•com>
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,
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devicetree@vger•kernel.org, kexec@lists•infradead.org
Subject: Re: [PATCH v9 4/5] arm64: kexec: Add support for crashkernel CMA reservation
Date: Mon, 23 Mar 2026 03:20:48 -0700 [thread overview]
Message-ID: <acETyW3FYaWCShUc@gmail.com> (raw)
In-Reply-To: <20260323072745.2481719-5-ruanjinjie@huawei.com>
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) <robh@kernel•org>
> Acked-by: Baoquan He <bhe@redhat•com>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel•org>
> Acked-by: Ard Biesheuvel <ardb@kernel•org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei•com>
> ---
> 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 */
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?
next prev parent reply other threads:[~2026-03-23 10:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 7:27 [PATCH v9 0/5] arm64/riscv: Add support for crashkernel CMA reservation Jinjie Ruan
2026-03-23 7:27 ` [PATCH v9 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr Jinjie Ruan
2026-03-23 7:27 ` [PATCH v9 2/5] crash: Exclude crash kernel memory in crash core Jinjie Ruan
2026-03-23 7:27 ` [PATCH v9 3/5] crash: Use crash_exclude_core_ranges() on powerpc Jinjie Ruan
2026-03-23 7:27 ` [PATCH v9 4/5] arm64: kexec: Add support for crashkernel CMA reservation Jinjie Ruan
2026-03-23 10:20 ` Breno Leitao [this message]
2026-03-23 11:17 ` Jinjie Ruan
2026-03-23 16:42 ` Breno Leitao
2026-03-23 7:27 ` [PATCH v9 5/5] riscv: " Jinjie Ruan
2026-03-23 16:55 ` [PATCH v9 0/5] arm64/riscv: " Andrew Morton
2026-03-24 4:02 ` Jinjie Ruan
2026-03-24 4:29 ` Sourabh Jain
2026-03-24 6:14 ` Jinjie Ruan
2026-03-24 6:35 ` Askar Safin
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