Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

Zachary Amsden
2007-03-20T19:54:27Z

Andi Kleen wrote:
> One thing I was pondering was to replace the expensive popfs with
>
> bt $IF,(%rsp)
> jnc 1f
> sti
> 1:
>
> But would be mostly a P4 optimization again and I'm not 100% sure it is
> worth it.
>

Worth it on 32-bit. On AMD64, probably not. On Intel 64-bit, maybe,
but less important than in P4 days.

This could change character completely if used at the tail of a function
where you now have

sti; 1: ret

Which generates an interrupt holdoff on the ret, an unusual thing to do.

Zach