Re: [PATCH -v2] x86/boot/compressed: Register dummy NMI handler in EFI boot loader, to avoid kdump crashes

[Zeng Heng]

On 2023/1/10 20:34, Ingo Molnar wrote:
> * Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> > > mce_panic -> panic -> __crash_kexec()
> > >
> > > Yes?
> > >
> > > If so, then we should make sure we have *exited* #MC context before calling
> > > panic() and not have to add hacks like this one of adding an empty NMI handler.
> > >
> > > But I'm only speculating as it is hard to make sense of all this text.
> > IOW, does this help?
> >
> > ---
> > diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> > index 7832a69d170e..55437d8a4fad 100644
> > --- a/arch/x86/kernel/cpu/mce/core.c
> > +++ b/arch/x86/kernel/cpu/mce/core.c
> > @@ -287,6 +287,7 @@ static noinstr void mce_panic(const char *msg, struct mce *final, char *exp)
> >   		if (panic_timeout == 0)
> >   			panic_timeout = mca_cfg.panic_timeout;
> >   		panic(msg);
> > +		mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);

I'm willing to test any patch provided, but the panic() is never return 
and the

mce_wrmsrl() would be never called. Am I wrong?

B.R.,

Zeng Heng

> So your suggestion was to exit MC context 'before' the panic() call - but
> the patch calls it 'after' - was that intentional?
>
> Thanks,
>
> 	Ingo