RE: [PATCH v5 20/34] x86/fred: add a machine check entry stub for FRED

[Li, Xin3]

> > Unlike IDT, no need to save/restore dr7 in FRED machine check handler.
> 
> Given how fragile MCE is, the question should be, do we ever want hw
> breakpoints to happen while it is running?

HW breakpoints still work if they are properly configured.

> If the hw-breakpoint handler trips on the same memory fail that got us into the
> mce the first time, we're dead.

Right.

Unless the MCIP bit is turned off any subsequent #MC goes to shutdown
("machine is screwed").

It's the kernel debugger's responsibility to decide how to proceed in such
cases. But if the kernel debugger itself is in a screwed memory region, we
are soooooo dead.

Thanks!
  Xin