Re: [patch 1/2] x86_64 page fault NMI-safe

Maciej W. Rozycki
2010-07-14T22:31:17Z

On Wed, 14 Jul 2010, Linus Torvalds wrote:

> You just count differently. I don't count the first one (the "real"
> NMI). That obviously happens. So I only count how many interrupts we
> need to fake. That's my "one". That's the one that happens as a result
> of the fault that we take on the iret in the emulated model.

Ah, I see -- so we are on the same page after all.

> (Yeah, yeah, you can call it a "one-bit counter", but I don't think
> that's a counter. It's just a bit of information).

Hardware has something like a strapped-high D flip-flop (NMI goes to the
clock input) with an extra reset input I presume -- this dates back to
8086 when the transistor count mattered with accuracy higher than 1e6. ;)

Maciej