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Date:	Wed, 23 Jul 2014 17:23:11 +0200
From:	Borislav Petkov <>
To:	Andy Lutomirski <>
Cc:	"H. Peter Anvin" <>,
	Linus Torvalds <>,
	"" <>,
	X86 ML <>
Subject: Re: STI architectural question (and lretq -- I'm not even kidding)

On Wed, Jul 23, 2014 at 08:12:32AM -0700, Andy Lutomirski wrote:
> How are we supposed to survive two machine checks in rapid succession?
> The second will fire as soon as the first one is acked, I imagine.
> Unless we switch stacks before acking the MCE, the return address of
> the first one will be lost.

Oh, that might not fly but in that case the box probably deserves to die

I was adressing what you said earlier: "But here's the problem: what
happens if an NMI or MCE happens between the sti and the lretq? I think
an MCE just might be okay -- it's not really recoverable anyway."

An MC Exception can be recoverable and we can recover. The fact that we
raise an exception doesn't always mean we die.


Sent from a fat crate under my desk. Formatting is fine.
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