From: Mike Rapoport <rppt@kernel•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,
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,
akpm@linux-foundation•org, bhe@redhat•com, vgoyal@redhat•com,
dyoung@redhat•com, rdunlap@infradead•org, pmladek@suse•com,
dapeng1.mi@linux•intel.com, kees@kernel•org, paulmck@kernel•org,
lirongqing@baidu•com, arnd@arndb•de, ardb@kernel•org,
leitao@debian•org, cfsworks@gmail•com, ryan.roberts@arm•com,
sourabhjain@linux•ibm.com, tangyouling@kylinos•cn,
eajames@linux•ibm.com, hbathini@linux•ibm.com,
ritesh.list@gmail•com, songshuaishuai@tinylab•org,
samuel.holland@sifive•com, kevin.brodsky@arm•com,
vishal.moola@gmail•com, junhui.liu@pigmoral•tech,
coxu@redhat•com, liaoyuanhong@vivo•com,
fuqiang.wang@easystack•cn, jbohac@suse•cz, brgerst@gmail•com,
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,
kexec@lists•infradead.org
Subject: Re: [PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation
Date: Wed, 25 Feb 2026 17:48:41 +0200 [thread overview]
Message-ID: <aZ8Z2WXw3QwaXRo8@kernel.org> (raw)
In-Reply-To: <20260224085342.387996-5-ruanjinjie@huawei.com>
On Tue, Feb 24, 2026 at 04:53:41PM +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: Ard Biesheuvel <ardb@kernel•org>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei•com>
> ---
> 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 | 8 +++++++-
> arch/arm64/mm/init.c | 5 +++--
> 3 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..497f63b76898 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..c8862a762eb3 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 */
> phys_addr_t start, end;
> u64 i;
>
> @@ -64,6 +64,12 @@ int arch_crash_populate_cmem(struct crash_mem *cmem)
> cmem->nr_ranges++;
> }
>
> + for (i = 0; i < crashk_cma_cnt; i++) {
> + cmem->ranges[cmem->nr_ranges].start = crashk_cma_ranges[i].start;
> + cmem->ranges[cmem->nr_ranges].end = crashk_cma_ranges[i].end;
> + cmem->nr_ranges++;
> + }
Why do we need to add cma ranges here? They are anyway will be excluded in
crash_exclude_core_ranges().
The same comment applies to riscv patch.
> return 0;
> }
> #endif
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 96711b8578fd..144e30fe9a75 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;
>
> static void __init arch_reserve_crashkernel(void)
> {
> + unsigned long long crash_base, crash_size, cma_size = 0;
> unsigned long long low_size = 0;
> - unsigned long long crash_base, crash_size;
> bool high = false;
> int ret;
>
> @@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void)
>
> ret = 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;
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> + reserve_crashkernel_cma(cma_size);
> }
>
> static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
> --
> 2.34.1
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2026-02-25 15:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-24 8:53 [PATCH v6 0/5] arm64/riscv: Add support for crashkernel CMA reservation Jinjie Ruan
2026-02-24 8:53 ` [PATCH v6 1/5] powerpc/crash: sort crash memory ranges before preparing elfcorehdr Jinjie Ruan
2026-02-25 3:15 ` Ritesh Harjani
2026-02-26 9:24 ` Baoquan He
2026-02-26 9:35 ` Jinjie Ruan
2026-02-24 8:53 ` [PATCH v6 2/5] crash: Exclude crash kernel memory in crash core Jinjie Ruan
2026-02-26 9:29 ` Baoquan He
2026-02-24 8:53 ` [PATCH v6 3/5] crash: Use crash_exclude_core_ranges() on powerpc Jinjie Ruan
2026-02-24 8:53 ` [PATCH v6 4/5] arm64: kexec: Add support for crashkernel CMA reservation Jinjie Ruan
2026-02-25 15:48 ` Mike Rapoport [this message]
2026-02-26 3:24 ` Jinjie Ruan
2026-02-26 9:33 ` Baoquan He
2026-02-24 8:53 ` [PATCH v6 5/5] riscv: " Jinjie Ruan
2026-02-25 15:50 ` [PATCH v6 0/5] arm64/riscv: " Mike Rapoport
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