linux-kernel - Re: [patch] i386: remove IOPL check on task switch

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Message-ID: <200611031902_MC3-1-D042-CA1E@compuserve.com>
Date:	Fri, 3 Nov 2006 19:00:11 -0500
From:	Chuck Ebbert <76306.1226@...puserve.com>
To:	Zachary Amsden <zach@...are.com>
Cc:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] i386: remove IOPL check on task switch

In-Reply-To: <454B850C.3050402@...are.com>

On Fri, 03 Nov 2006 10:06:04 -0800, Zachary Amsden wrote:

> Chuck Ebbert wrote:
> > IOPL is implicitly saved and restored on task switch,
> > so explicit check is no longer needed.
> 
> Nack.  This is used for paravirt-ops kernels that use IOPL'd userspace.  

How does that work?  In the stock kernel, anything done by
the call to set_iopl_mask() (that was removed by the patch)
will be nullified by the 'popfl' at the end of the switch_to()
macro.

-- 
Chuck
"Even supernovas have their duller moments."
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