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

[dmukhin@xxxxxxxx]

On Wed, Aug 12, 2026 at 10:19:55AM +0200, Jan Beulich wrote:
> 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, dmukhin@xxxxxxxx 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, dmukhin@xxxxxxxx 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?)

I did not find '?' being used, will update the key mapping.

Thanks for the suggestion!

> 
> Jan
>