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Subject: Re: [patch, 2.6.10-rc3] safe_hlt() & NMIs
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Ingo Molnar <mingo@elte.hu>, Lee Revell <rlrevell@joe-job.com>,
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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. 

Alan