From mboxrd@z Thu Jan  1 00:00:00 1970
From: james.morse@arm.com (James Morse)
Date: Fri, 16 Sep 2016 17:08:28 +0100
Subject: [PATCH v26 6/7] arm64: kdump: update a kernel doc
In-Reply-To: <20160907042908.6232-7-takahiro.akashi@linaro.org>
References: <20160907042908.6232-1-takahiro.akashi@linaro.org>
 <20160907042908.6232-7-takahiro.akashi@linaro.org>
Message-ID: <57DC18FC.9000807@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Akashi,

On 07/09/16 05:29, AKASHI Takahiro wrote:
> This patch adds arch specific descriptions about kdump usage on arm64
> to kdump.txt.

> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt

> @@ -249,6 +249,13 @@ Dump-capture kernel config options (Arch Dependent, arm)
>  
>      AUTO_ZRELADDR=y
>  
> +Dump-capture kernel config options (Arch Dependent, arm64)
> +----------------------------------------------------------
> +
> +- Please note that kvm of the dump-capture kernel will not be enabled
> +  on non-VHE systems even if it is configured. This is because the CPU
> +  cannot be reset to EL2 on panic.

Nit:
cannot be -> will not be

We could try to do this, but its more code that could prevent us reaching the
kdump kernel, so we choose not to.


> @@ -370,6 +381,9 @@ For s390x:
>  For arm:
>  	"1 maxcpus=1 reset_devices"
>  
> +For arm64:
> +	"1 maxcpus=1 reset_devices"
> +

'maxcpus=1' is a bit fragile. Since 44dbcc93ab67145 ("arm64: Fix behavior of
maxcpus=N") udev on ubuntu vivid (running on Juno) has taken it upon itself to
bring the secondary cores online, even when booted with 'maxcpus=1'.

Can we change the recomendation to "1 nosmp reset_devices"?


Thanks,

James