Re: [PATCH v3] xen/common: add keyhandler to show Xen command line

On 12.08.2026 10:03, Roger Pau Monné wrote:
> On Wed, Aug 12, 2026 at 09:28:46AM +0200, Jan Beulich wrote:
>> On 11.08.2026 22:56, [email protected] wrote:
>>> On Tue, Aug 11, 2026 at 10:05:17AM +0200, Roger Pau Monné wrote:
>>>> On Mon, Aug 10, 2026 at 04:04:01PM -0700, [email protected] wrote:
>>>>> +static int __init cf_check misc_init(void)
>>>>> +{
>>>>> +    register_keyhandler('X', show_hypervisor_info,
>>>>> +                        "show hypervisor information", 0);
>>>>
>>>> "show hypervisor information" seems too generic to me, almost all
>>>> debug keys could be defined by this sentence TBH.  I think this needs
>>>> to be more specific, but I'm not sure what's the plan regarding this
>>>> key.  Is there an intention to print more stuff here, or just the
>>>> command line?  Knowing the full set of information to be printed might
>>>> help come up with a better name.
>>>
>>> I will update to "show_cmdline" since I originally planed to expose Xen
>>> command line only so it is possible to better debug a system when dom0
>>> becomes almost unresponsive.
>>
>> Yet as indicated already on v1 (I think) - a precious debug key character
>> for just the command line seems rather wasteful to me. If it's only the
>> command line, and if that _really_ needs exposing via a debug key (i.e.
>> if there are reasonable scenarios where "xl info" cannot be used), perhaps
>> attach it to e.g. the 'h' key output?
> 
> I was going to say that we should not overload the 'h' key with
> printing a possibly long string, but I see we already print a bunch of
> information there, like the buildid and the compiler banner.
> 
> One option would be to introduce a new debug character, and move the
> printing of the buildid and the banner to that key, together with the
> command line.  Then 'h' output will be cleaner and just print the list
> of installed handlers.  That would give the new key more content, and
> help cleanup the output from the 'h' debug key at the same time.

Hmm, yes, that's definitely an option. May I then further suggest to use
'?' as the key for this? (Or am I overlooking that key already being in
use somewhere?)

Jan