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RE: [Xen-devel] [PATCH] small adjustment to asm constraintsforc/s19400

To: "Guanqun Lu" <guanqun.lu@xxxxxxxxx>, "Kevin Tian" <kevin.tian@xxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] small adjustment to asm constraintsforc/s19400
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Tue, 31 Mar 2009 11:54:34 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, KeirFraser <keir.fraser@xxxxxxxxxxxxx>
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>>> "Tian, Kevin" <kevin.tian@xxxxxxxxx> 31.03.09 12:21 >>>
>BTW, another question comes when I'm clearing the code.
>in load_segments, fs/gs base MSRs are only updated for non 32-on-64
>domain. I guess that it's just for performance reason as 32bit guest 
>doesn't require to switch gs base. I want to get your confirmation 
>since in current low level context S3 resume code, we always restore 
>those base MSRs even for 32-on-64 case.

Correct - your code isn't performance sensitive, so keeping it simple is
probably preferable. load_segments() sits in the context switch code, and
thus it tries to avoid things not needed for a particular guest.

Jan


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