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

Linus Torvalds
2010-07-18T18:23:26Z

On Sun, Jul 18, 2010 at 11:04 AM, Avi Kivity <avi@redhat.com> wrote:
>
> Too simple - an MCE will switch to its own stack, failing the test.  Now
> that we have correctable MCEs, that's not a good idea.

Ahh, true. And I think we do DEBUG traps with IST too.

So we do need the explicit flag over the region. Too bad. I was hoping
to handle the nested case without having to set up the percpu segment
(that whole conditional swapgs thing, which is extra painful in NMI).

And at that point, if you require the separate flag anyway, the %rsp
range test is equivalent to the %rip range test.

Linus