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Date: Mon, 21 Feb 2022 11:48:49 +0800
From: Baoquan He <bhe@...hat.com>
To: Zhen Lei <thunder.leizhen@...wei.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
linux-kernel@...r.kernel.org, Dave Young <dyoung@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
kexec@...ts.infradead.org,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
Rob Herring <robh+dt@...nel.org>,
Frank Rowand <frowand.list@...il.com>,
devicetree@...r.kernel.org, Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>,
Feng Zhou <zhoufeng.zf@...edance.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
Chen Zhou <dingguo.cz@...group.com>,
John Donnelly <John.p.donnelly@...cle.com>,
Dave Kleikamp <dave.kleikamp@...cle.com>
Subject: Re: [PATCH v20 5/5] kdump: update Documentation about crashkernel
On 01/24/22 at 04:47pm, Zhen Lei wrote:
> From: Chen Zhou <chenzhou10@...wei.com>
>
> For arm64, the behavior of crashkernel=X has been changed, which
> tries low allocation in DMA zone and fall back to high allocation
> if it fails.
>
> We can also use "crashkernel=X,high" to select a high region above
> DMA zone, which also tries to allocate at least 256M low memory in
> DMA zone automatically and "crashkernel=Y,low" can be used to allocate
> specified size low memory.
>
> So update the Documentation.
>
> Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
> Documentation/admin-guide/kdump/kdump.rst | 11 +++++++++--
> Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
> 2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index cb30ca3df27c9b2..d4c287044be0c70 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -361,8 +361,15 @@ Boot into System Kernel
> kernel will automatically locate the crash kernel image within the
> first 512MB of RAM if X is not given.
>
> - On arm64, use "crashkernel=Y[@X]". Note that the start address of
> - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
> + On arm64, use "crashkernel=X" to try low allocation in DMA zone and
> + fall back to high allocation if it fails.
> + We can also use "crashkernel=X,high" to select a high region above
> + DMA zone, which also tries to allocate at least 256M low memory in
> + DMA zone automatically.
> + "crashkernel=Y,low" can be used to allocate specified size low memory.
> + Use "crashkernel=Y@X" if you really have to reserve memory from
> + specified start address X. Note that the start address of the kernel,
> + X if explicitly specified, must be aligned to 2MiB (0x200000).
Hmm, we may not need the details related to crashkernel,high|low in this
section. This just gives examples of basic configation for each ARCH.
The detailed configuration of all crashkernel setting can be found in
"crashkernel syntax" section, I don't think arm64 is so special to need
a specific one.
>
> Load the Dump-capture Kernel
> ============================
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f5a27f067db9ed9..65780c2ca830be0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -792,6 +792,9 @@
> [KNL, X86-64] Select a region under 4G first, and
> fall back to reserve region above 4G when '@...set'
> hasn't been specified.
> + [KNL, ARM64] Try low allocation in DMA zone and fall back
> + to high allocation if it fails when '@...set' hasn't been
> + specified.
> See Documentation/admin-guide/kdump/kdump.rst for further details.
How about add ARM64 like below to avoid redundant words?
[KNL, X86-64, ARM64] Select a region under 4G first, and
fall back to reserve region above 4G when '@...set'
hasn't been specified.
>
> crashkernel=range1:size1[,range2:size2,...][@offset]
> @@ -808,6 +811,8 @@
> Otherwise memory region will be allocated below 4G, if
> available.
> It will be ignored if crashkernel=X is specified.
> + [KNL, ARM64] range in high memory.
> + Allow kernel to allocate physical memory region from top.
Ditto, please don't add redundent words if it's similar to x86_64
handling.
> crashkernel=size[KMG],low
> [KNL, X86-64] range under 4G. When crashkernel=X,high
> is passed, kernel could allocate physical memory region
> @@ -816,13 +821,15 @@
> requires at least 64M+32K low memory, also enough extra
> low memory is needed to make sure DMA buffers for 32-bit
> devices won't run out. Kernel would try to allocate at
> - at least 256M below 4G automatically.
> + least 256M below 4G automatically.
> This one let user to specify own low range under 4G
> for second kernel instead.
> 0: to disable low allocation.
> It will be ignored when crashkernel=X,high is not used
> or memory reserved is below 4G.
> -
> + [KNL, ARM64] range in low memory.
> + This one let user to specify a low range in DMA zone for
> + crash dump kernel.
Ditto.
> cryptomgr.notests
> [KNL] Disable crypto self-tests
>
> --
> 2.25.1
>
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