linux-kernel - Re: Sysenter crash with Nested Task Bit set

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Message-ID: <Pine.LNX.4.64.0609180904360.4388@g5.osdl.org>
Date:	Mon, 18 Sep 2006 09:10:29 -0700 (PDT)
From:	Linus Torvalds <torvalds@...l.org>
To:	Andi Kleen <ak@...e.de>
cc:	Andrew Morton <akpm@...l.org>,
	Chuck Ebbert <76306.1226@...puserve.com>,
	In Cognito <defend.the.world@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, bcrl@...ck.org,
	Zachary Amsden <zach@...are.com>
Subject: Re: Sysenter crash with Nested Task Bit set

On Mon, 18 Sep 2006, Linus Torvalds wrote:
> 
> The addition is fairly obvious, but maybe I screwed something up, so buyer 
> beware...

Final note (I promise): now that we save/restore eflags again, we 
should probably revert the set_iopl_mask() in task switching too. However, 
that apparently has some para-virtualization issues, so I'm going to 
ignore that part from now.

However, I'd really like people who know and care about the 
paravirtualization to take a good long look at it: because right now, with 
the addition of the eflags save/restore, the set_iopl_mask() in 
__switch_to() is entirely useless for non-virtualized environments, afaik.

Zack added to the cc. Who else needs to know?

		Linus
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