[Skiboot] [PATCH v2 2/2] core: Implement non-FSP dump region opal call

[Vasant Hegde]

On 05/07/2019 06:16 AM, Joel Stanley wrote:
> Digging this back up again as it would have been handy for some
> debugging yesterday.
> 
> On Mon, 28 May 2018 at 13:19, Benjamin Herrenschmidt
> <benh at kernel.crashing.org> wrote:
>>
>> On Mon, 2018-05-28 at 13:25 +0930, Joel Stanley wrote:
>>> This provides an implementation of the OPAL_REGISTER_DUMP_REGION and
>>> OPAL_UNREGISTER_DUMP_REGION calls that can be used by non-FSP systems,
>>> and performs that registration for all astbmc platforms.
>>>
>>> This pointer will be used by eg. pdbg to fetch the host kernel's log
>>> buffer over FSI.
>>>
>>> We unconditionally clear the value on a reboot (both fast-reboot and
>>> reliable reboot) to reduce the chance of debug tools getting the wrong
>>> buffer.
>>
>> I wouldn't make it BMC specific.
>>
>> Instead, I would suggest you:
>>
>>   - Add "generic" OPAL calls that populate the debug descritor (ie,
>> statically defined using OPAL_CALL).
>>
>>   - Make the above call an optional machine.register_dump_region
>>
>>   - Make FSP machines populate the above to *also* register with the
>> FSP.
>>
>> That way we can also use/create similar tools (or just getmemproc) to
>> get to the kernel dmesg via the debug descriptor on FSP systems.
> 
> Oliver, Vasant: are you happy with the patch as-is? Or shall we go
> down the route that benh suggested?

Benh suggestion is better.

> 
> The advantage of the patch as-is is existing kernels that boot on new
> skiboot will register the debug descriptor.

Even with new approach we will not have kernel changes right.

-Vasant