From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E92B72D249E; Wed, 28 Jan 2026 08:32:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769589124; cv=none; b=GzYg8O0wVlxm/wYdJyeysBUPxeHcLunyHlg9RzSyrvlmxsZvP0G5/KtxOMFFXcX1BIii4tJkJabnCPsBSP5UDwZn2Okpm6lj8gVDuc69XHOHVNpEyCAdZUalNSVf2iUrqoBhpG9eMbnPNftQfTS3OOnMIs0FUaOeI4WXXnvCul8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769589124; c=relaxed/simple; bh=MIu53TNJT0oYRJMg60HbP3DOZ0cZyH4Xd+NMgQs6Nec=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=H4lItjoJmAT+KoqFTgYH5hE7lbJM1n84uSREDIVx+GeDRXV8tm8E3pXnutwedg2Z1xqWCLerqoR7pHL+PrtZiiPqKg8DvgDO8hEjJYTLnCtKksBdgXB2mrYJ5SdHbvgXNL4A/e6QumQBf/sQDQdFNaWvjlECL2Kz4ldP9CKRETo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bw/oUTvh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bw/oUTvh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00DD4C4CEF1; Wed, 28 Jan 2026 08:31:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769589123; bh=MIu53TNJT0oYRJMg60HbP3DOZ0cZyH4Xd+NMgQs6Nec=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bw/oUTvhB6gWXSudQa1AB0m+S9WAXgkPU6Njvqa4zFpA23y9kpL8zHHiXOOelOIuj Wrwdx5cmCXxnvnBe9jGMNxWBZ+tMMVAkXuL6xoblNIfeQVy+h2ujR3bCqqjZEkheWb TbviHdHpUdYiuSyCqAEYkFOnTVKFrRejH3+BBFuEOauCgYpiVM+ynpCT5njyqaPCSR zdiy6aUHyDTeA4SlhajejnJDWljHJ8Mv+kpD6Ebf53Jh+SJQcuvFMMMWRd/csBMYxE E0nxvWdxUbtfAnTpKYwZEp9lUiNfgdl4F7NvgH27OUXiVGasrmu31TrM/SQwi5e+Xt Fnxac7mac9+UQ== Date: Wed, 28 Jan 2026 10:31:51 +0200 From: Mike Rapoport To: Jinjie Ruan Cc: ardb@kernel.org, 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@kernel.org, elver@google.com, arnd@arndb.de, fvdl@google.com, lirongqing@baidu.com, bhelgaas@google.com, bhe@redhat.com, dave.hansen@linux.intel.com, cfsworks@gmail.com, osandov@fb.com, sourabhjain@linux.ibm.com, jbohac@suse.cz, ryan.roberts@arm.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] arm64: kexec: Add support for crashkernel CMA reservation Message-ID: References: <20260126081334.699147-1-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: <20260126081334.699147-1-ruanjinjie@huawei.com> On Mon, Jan 26, 2026 at 04:13:34PM +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. > > Update kernel-parameters.txt to document CMA support for crashkernel on > arm64 architecture. I'm looking at this and at almost identical patch for riscv https://lore.kernel.org/all/20260126080738.696723-1-ruanjinjie@huawei.com and it feels wrong that we have duplicate the code that excludes cma ranges. CMA ranges are known to the crash_core and I don't see why we cannot exclude them there. > 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(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt 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=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 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 long *sz) > u64 i; > phys_addr_t start, end; > > - nr_ranges = 2; /* for exclusion of crashkernel region */ > + nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */ > for_each_mem_range(i, &start, &end) > nr_ranges++; > > @@ -64,6 +64,12 @@ static int prepare_elf_headers(void **addr, unsigned long *sz) > 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++; > + } > + > /* Exclude crashkernel region */ > ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end); > if (ret) > @@ -75,6 +81,13 @@ static int prepare_elf_headers(void **addr, unsigned long *sz) > goto out; > } > > + for (i = 0; i < crashk_cma_cnt; ++i) { > + ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start, > + crashk_cma_ranges[i].end); > + if (ret) > + goto out; > + } > + > ret = crash_prepare_elf64_headers(cmem, true, addr, sz); > > 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; > > 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.