Re: [patch, 2.6.10-rc3] safe_hlt() & NMIs

From: Zwane Mwaikambo
Date: Wed Dec 15 2004 - 21:24:09 EST

On Thu, 16 Dec 2004, Alan Cox wrote:

> On Maw, 2004-12-14 at 23:09, Linus Torvalds wrote:
> > On Tue, 14 Dec 2004, Ingo Molnar wrote:
> > Now that you mention it, I have this dim memory of the one-instruction
> > "sti-shadow" actually disabling NMI's (and debug traps) too. The CPU
> > literally doesn't test for async events following "sti".
> >
> > Or maybe that was "mov->ss". That one also has that strange "black hole"
> > for one instruction.
> The mov to ss one is a bit more magic than that however. If you write
> 3Gb of mov->ss into memory (ie about 64 pages to thrash the cache and
> slow it plus mmap repeatedly) and run it you don't get a vastly long irq
> delay at least on intel, not tried the others.

Might this be because you can't rely on interrupt suppression for back to
back suppressing instructions?

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