Re: [PATCH 4/4] x86 paravirt_ops: binary patching infrastructure

[Jeremy Fitzhardinge]

Andi Kleen wrote:
> >  
> > +#ifdef CONFIG_PARAVIRT
> > +void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end)
> >     
>
> It would be better to merge this with the existing LOCK prefix patching
> or perhaps the normal alternative() patcher (is there any particular
> reason you can't use it?)
>
> Three alternative patching mechanisms just seems to be too many

The difference is that every hypervisor wants its own patched 
instruction sequence, which may require a specialized patching 
mechanism.  If you're simply patching in calls, then it isn't a big 
deal, but you may also want to patch in real inlined code for some 
operations (like sti/cli equivalents).  The alternatives are to allow 
each backend to deal with its own patching (perhaps with common 
functions abstracted out as they appear), or have a common set of 
patching machinery which can deal with all users.  The former seems simpler.

   J
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