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

From: Andi Kleen <[email-masked]>
Date: 20 Mar 2007 21:02:42 +0100

> 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