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

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.


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