Re: [Xen-devel] Boot Linux on PVH guest via OVMF/UEFI issues

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.03.19 at 18:40, <anthony.perard@xxxxxxxxxx> wrote:
> # About the guest crash without error messages
> 
> I had a guest crash just after systemd started to print messages on the
> console. But neither Linux nor Xen had printed anything about why the
> guest crash. No amount of command line options helped.
> 
> I've managed to have Linux print the error message on panic, but I had
> to make a modification so that Linux would not tell Xen when a crash
> happened. This patch:
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -277,8 +277,6 @@ void xen_emergency_restart(void)
>  static int
>  xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
>  {
> -       if (!kexec_crash_loaded())
> -               xen_reboot(SHUTDOWN_crash);
>         return NOTIFY_DONE;
>  }
> 
> Is it possible in the future for the kernel to actually write panic
> message before Xen destroy the domain?

Just the day before yesterday I've run into a (deliberately)
panic()-ing DomU, and it _did_ log the panic output. So it's
likely not as simple as a boolean does / doesn't log messages?
Of course in my case it was a PV DomU, and started with -c
rather than the possibly more common -V, which may already
account for the difference. I.e. I wonder whether there's
too much of a delay for the output to actually make it out in
some cases. And if so, it might not even be the kernel's
"fault".

Jan



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