> > > i thought task switch using tss was rather slower.  have you measured?
> > 
> > Btw, if we want to speed up the syscall path, we should be using sysenter/
> > sysret on P4s. This is actually most efficiently supported with a
> > per-CPU TSS. Otherwise, you need to do a wrmsr for each context
> > switch, and wrmsr is very slow.
> 
> why do you think wrmsr is needed?
> even with per-cpu TSS, all you need is copying esp into
> somewhere pointed by SYSENTER_ESP, isn't it?

i meant, s/per-cpu/per-process/.

YAMAMOTO Takashi