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

Andi Kleen
2007-03-20T20:02:45Z

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

Well most of Intel 64bit is P4 -- and Intel is still shipping
millions more of them each quarter.

> 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.

Unusual yes, but I don't see how it should cause problems. Or do you
have anything specific in mind?

Worse is probably that on K8 this case might cause a pipeline stall
if there isn't a prefix in front of the ret.

-Andi