Re: [PATCH] 3/5 explicit-iopl

[Andi Kleen]

zach@xxxxxxxxxx writes:
> 
> Unfortunately, this added one field to the thread_struct.  But as a bonus, on
> P4, the fastest time measured for switch_to() went from 312 to 260 cycles, a
> win of about 17% in the fast case through this performance critical path.

Cool! Definitely want this on x86-64 too.

Can we perhaps get rid of the PUSHF/POPF in the SYSENTER syscall path too?
iirc they were only for single stepping. But SYSENTER doesn't disable
single stepping, so the debug handler could detect this and set
some magic flag that restores it on syscall exit.

-Andi
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