Re: [PATCH v3] xen: add support for automatic debug key actions in case of crash

[Julien Grall <julien@xxxxxxx>]

Hi,

Sorry for jumping late in the discussion.

On 26/11/2020 11:20, Jan Beulich wrote:
> On 26.11.2020 09:03, Juergen Gross wrote:
> > When the host crashes it would sometimes be nice to have additional
> > debug data available which could be produced via debug keys, but
> > halting the server for manual intervention might be impossible due to
> > the need to reboot/kexec rather sooner than later.
> >
> > Add support for automatic debug key actions in case of crashes which
> > can be activated via boot- or runtime-parameter.
> >
> > Depending on the type of crash the desired data might be different, so
> > support different settings for the possible types of crashes.
> >
> > The parameter is "crash-debug" with the following syntax:
> >
> >    crash-debug-<type>=<string>
> >
> > with <type> being one of:
> >
> >    panic, hwdom, watchdog, kexeccmd, debugkey
> >
> > and <string> a sequence of debug key characters with '+' having the
> > special semantics of a 10 millisecond pause.
> >
> > So "crash-debug-watchdog=0+0qr" would result in special output in case
> > of watchdog triggered crash (dom0 state, 10 ms pause, dom0 state,
> > domain info, run queues).
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> > V2:
> > - switched special character '.' to '+' (Jan Beulich)
> > - 10 ms instead of 1 s pause (Jan Beulich)
> > - added more text to the boot parameter description (Jan Beulich)
> >
> > V3:
> > - added const (Jan Beulich)
> > - thorough test of crash reason parameter (Jan Beulich)
> > - kexeccmd case should depend on CONFIG_KEXEC (Jan Beulich)
> > - added dummy get_irq_regs() helper on Arm
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Except for the Arm aspect, where I'm not sure using
> guest_cpu_user_regs() is correct in all cases,
I am not entirely sure to understand what get_irq_regs() is supposed to 
returned on x86. Is it the registers saved from the most recent exception?
Cheers,


--
Julien Grall