Messages in this thread | | | Date | Mon, 8 Sep 2003 15:05:43 +0100 | From | Jamie Lokier <> | Subject | Re: [PATCH] Pentium Pro - sysenter - doublefault |
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Pavel Machek wrote: > > "SEP is unsupported". It's interesting that Pentium Pro erratum #82 > > is "SYSENTER/SYSEXIT instructions can implicitly load 'null segment > > selector' to SS and CS registers", implying that SYSENTER does > > _something_ useful on PPros. > > Well, with CS==0 machine is not going to survive too long. > If it only happens sometimes you might catch the double fault > and fixup, but....
The erratum only applies when you load CS==0 _deliberately_, by setting the MSR to that.
I'm wondering what happens when you don't do silly things - what is the undocumented behaviour of SYSENTER/SYSEXIT on those chips?
I vaguely recall reading details about the behaviour change made by Intel, around the time it was done, but I can't see to find it anywhere.
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