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Message-ID: <20210218083822.GL2871@MiWiFi-R3L-srv>
Date: Thu, 18 Feb 2021 16:40:06 +0800
From: Baoquan He <bhe@...hat.com>
To: Chen Zhou <chenzhou10@...wei.com>
Cc: mingo@...hat.com, tglx@...utronix.de, rppt@...nel.org,
dyoung@...hat.com, catalin.marinas@....com, will@...nel.org,
nsaenzjulienne@...e.de, corbet@....net, John.P.donnelly@...cle.com,
prabhakar.pkin@...il.com, horms@...ge.net.au, robh+dt@...nel.org,
arnd@...db.de, james.morse@....com, xiexiuqi@...wei.com,
guohanjun@...wei.com, huawei.libin@...wei.com,
wangkefeng.wang@...wei.com, linux-doc@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
kexec@...ts.infradead.org
Subject: Re: [PATCH v14 11/11] kdump: update Documentation about crashkernel
On 01/30/21 at 03:10pm, Chen Zhou wrote:
> 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.
Nice document adding which also takes care of x86 code implementation,
thanks. By the way, maybe you can remove John's 'Tested-by' since it
doesn't make much sense to test a document patch.
Acked-by: Baoquan He <bhe@...hat.com>
>
> Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
> Tested-by: John Donnelly <John.p.donnelly@...cle.com>
> ---
> Documentation/admin-guide/kdump/kdump.rst | 22 ++++++++++++++++---
> .../admin-guide/kernel-parameters.txt | 11 ++++++++--
> 2 files changed, 28 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 75a9dd98e76e..0877c76f8015 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -299,7 +299,16 @@ Boot into System Kernel
> "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
> starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
>
> - On x86 and x86_64, use "crashkernel=64M@16M".
> + On x86 use "crashkernel=64M@16M".
> +
> + On x86_64, use "crashkernel=X" to select a region under 4G first, and
> + fall back to reserve region above 4G. And go for high allocation
> + directly if the required size is too large.
> + We can also use "crashkernel=X,high" to select a region above 4G, which
> + also tries to allocate at least 256M below 4G automatically and
> + "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.
>
> On ppc64, use "crashkernel=128M@32M".
>
> @@ -316,8 +325,15 @@ 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).
>
> Load the Dump-capture Kernel
> ============================
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index a10b545c2070..908e5c8b61ba 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -738,6 +738,9 @@
> [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.
>
> crashkernel=range1:size1[,range2:size2,...][@offset]
> @@ -754,6 +757,8 @@
> 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.
> crashkernel=size[KMG],low
> [KNL, X86-64] range under 4G. When crashkernel=X,high
> is passed, kernel could allocate physical memory region
> @@ -762,13 +767,15 @@
> 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.
> cryptomgr.notests
> [KNL] Disable crypto self-tests
>
> --
> 2.20.1
>
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