linux-kernel - Re: [PATCH v10 5/5] kdump: update Documentation about crashkernel on arm64

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Message-ID: <20200703044635.GA28640@dhcp-128-65.nay.redhat.com>
Date:   Fri, 3 Jul 2020 12:46:35 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Chen Zhou <chenzhou10@...wei.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bhe@...hat.com,
        catalin.marinas@....com, will@...nel.org, james.morse@....com,
        robh+dt@...nel.org, arnd@...db.de, John.P.donnelly@...cle.com,
        prabhakar.pkin@...il.com, nsaenzjulienne@...e.de, corbet@....net,
        bhsharma@...hat.com, horms@...ge.net.au, guohanjun@...wei.com,
        xiexiuqi@...wei.com, huawei.libin@...wei.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kexec@...ts.infradead.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v10 5/5] kdump: update Documentation about crashkernel on
 arm64

Hi,

Thanks for the update, but still some nitpicks :(

I'm sorry I did not catch them previously,  but maybe it is not worth to
repost the whole series if no other changes needed.
On 07/03/20 at 11:58am, Chen Zhou wrote:
> Now we support crashkernel=X,[low] on arm64, update the Documentation.
> We could use parameters "crashkernel=X crashkernel=Y,low" to reserve
> memory above 4G.
> 
> Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
> Tested-by: John Donnelly <John.p.donnelly@...cle.com>
> Tested-by: Prabhakar Kushwaha <pkushwaha@...vell.com>
> ---
>  Documentation/admin-guide/kdump/kdump.rst       | 14 ++++++++++++--
>  Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++--
>  2 files changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 2da65fef2a1c..e80fc9e28a9a 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -299,7 +299,15 @@ 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=Y" to select a region under 4G first, and
> +   fall back to reserve region above 4G.
> +   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 we really have to reserve memory from specified

s/we/you

> +   start address X.
>  
>     On ppc64, use "crashkernel=128M@32M".
>  
> @@ -316,8 +324,10 @@ 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
> +   On arm64, use "crashkernel=Y[@X]". Note that the start address of
>     the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
> +   If crashkernel=Z,low is specified simultaneously, reserve spcified size

s/spcified/specified

> +   low memory firstly and then reserve memory above 4G.
>  
>  Load the Dump-capture Kernel
>  ============================
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index fb95fad81c79..58a731eed011 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -722,6 +722,9 @@
>  			[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] If crashkernel=X,low is specified, reserve
> +			spcified size low memory firstly, and then reserve memory

s/spcified/specified

> +			above 4G.
>  			See Documentation/admin-guide/kdump/kdump.rst for further details.
>  
>  	crashkernel=range1:size1[,range2:size2,...][@offset]
> @@ -746,13 +749,23 @@
>  			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 under 4G.
> +			This one let user to specify own low range under 4G

s/own low/a low

> +			for crash dump kernel instead.
> +			Be different from x86_64, kernel reserves specified size
> +			physical memory region only when this parameter is specified
> +			instead of trying to reserve at least 256M below 4G
> +			automatically.
> +			Use this parameter along with crashkernel=X when we want
> +			to reserve crashkernel above 4G. If there are devices
> +			need to use ZONE_DMA in crash dump kernel, it is also
> +			a good choice.
>  	cryptomgr.notests
>  			[KNL] Disable crypto self-tests
>  
> -- 
> 2.20.1
>