Re: [RFC] #MC mess

From: Peter Zijlstra
Date: Tue Feb 18 2020 - 15:02:21 EST

On Tue, Feb 18, 2020 at 06:20:38PM +0000, Luck, Tony wrote:
> > Anything else I'm missing? It is likely...
> + hw_breakpoint_disable();
> + static_key_disable(&__tracepoint_read_msr.key);
> + tracing_off();
> +
> ist_enter(regs);
> How about some code to turn all those back on for a recoverable (where we actually recovered) #MC?

Then please rewrite the #MC entry code to deal with nested exceptions
unmasking the MCE, very similr to NMI.

The moment you allow tracing, jump_labels or anything else you can
expect #PF, #BP and probably #DB while inside #MC, those will then IRET
and re-enable the #MC.

The current situation is completely and utterly buggered.