Subject: [PATCH v12 14/16] arm64: kdump: update a kernel doc

From: [email-masked] (AKASHI Takahiro)
Date: Wed, 16 Dec 2015 14:48:13 +0900

On 12/16/2015 02:17 AM, Will Deacon wrote:
> On Tue, Nov 24, 2015 at 10:25:34PM +0000, Geoff Levand wrote:
>> From: AKASHI Takahiro <[email-masked]>
>>
>> This patch adds arch specific descriptions about kdump usage on arm64
>> to kdump.txt.
>>
>> Signed-off-by: AKASHI Takahiro <[email-masked]>
>> ---
>>   Documentation/kdump/kdump.txt | 32 +++++++++++++++++++++++++++++++-
>>   1 file changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
>> index bc4bd5a..7d3fad0 100644
>> --- a/Documentation/kdump/kdump.txt
>> +++ b/Documentation/kdump/kdump.txt
>> @@ -18,7 +18,7 @@ memory image to a dump file on the local disk, or across the network to
>>   a remote system.
>>
>>   Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
>> -s390x and arm architectures.
>> +s390x, arm and arm64 architectures.
>>
>>   When the system kernel boots, it reserves a small section of memory for
>>   the dump-capture kernel. This ensures that ongoing Direct Memory Access
>> @@ -249,6 +249,29 @@ Dump-capture kernel config options (Arch Dependent, arm)
>>
>>       AUTO_ZRELADDR=y
>>
>> +Dump-capture kernel config options (Arch Dependent, arm64)
>> +----------------------------------------------------------
>> +
>> +1) Disable symmetric multi-processing support under "Processor type and
>> +   features":
>> +
>> +   CONFIG_SMP=n
>> +
>> +   (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
>> +   when loading the dump-capture kernel, see section "Load the Dump-capture
>> +   Kernel".)
>
> SMP is now forced on, so please update this text.

OK, I will fix it.

>> +2) The maximum memory size on the dump-capture kernel must be limited by
>> +   specifying:
>> +
>> +   mem=X[MG]
>> +
>> +   where X should be less than or equal to the size in "crashkernel="
>> +   boot parameter. Kexec-tools will automatically add this.
>> +
>> +3) Currently, kvm will not be enabled on the dump-capture kernel even
>> +   if it is configured.
>> +
>>   Extended crashkernel syntax
>>   ===========================
>>
>> @@ -312,6 +335,8 @@ Boot into System Kernel
>>      any space below the alignment point may be overwritten by the dump-capture kernel,
>>      which means it is possible that the vmcore is not that precise as expected.
>>
>> +   On arm64, use "crashkernel=Y[@X]".  Note that the start address of
>> +   the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
>>
>>   Load the Dump-capture Kernel
>>   ============================
>> @@ -334,6 +359,8 @@ For s390x:
>>   	- Use image or bzImage
>>   For arm:
>>   	- Use zImage
>> +For arm64:
>> +	- Use vmlinux
>
> What? Why doesn't Image work?

Actually it depends on kexec-tools, not the kernel.
Initially Geoff implemented vmlinux support only, then
recently Pratyush (RedHat) gave us a patch for "Image" support.

So now Image should work.

-Takahiro AKASHI

> Will