Re: [PATCH 3/25][V3] irq_flags / halt routines

[Glauber de Oliveira Costa]

Avi Kivity escreveu:
> Glauber de Oliveira Costa wrote:
> > Andi Kleen escreveu:
> > > On Wed, Aug 15, 2007 at 11:18:25AM -0300, Glauber de Oliveira Costa 
> > > wrote:
> > > > > Didn't we agree this should be a pvops client?
> > > > >
> > > > > -Andi
> > > > No. I exposed my reasoning, asked you back, but got no answer.
> > > > I'll do it again:
> > > >
> > > > This operations are just manipulating bits, and are doing no
> > > > privileged operations at all. Nothing that can be paravirtualized, in
> > >
> > > It's talking to a Hypervisor. That is privileged enough.
> > > Please do that change. If you add so many more ifdefs it's your
> > > duty to keep the overall number low.
> >
> > Again, this is the code of such function:
> >
> > static inline int raw_irqs_disabled_flags(unsigned long flags)
> > {
> >         return !(flags & X86_EFLAGS_IF);
> > }
> > so all it is doing is getting a parameter (flags), and bitmasking it. 
> > It is not talking to any hypervisor. I can't see your point. Unless 
> > you are
> > arguing that it _should_ be talking to a hypervisor. Is that your point?
>
> It is talking to a hypervisor.  This hypervisor does full 
> virtualization, except that it allows the guest to hide eflags.IF inside 
> eflags.AC as an optimization (otherwise you need to do binary 
> translation to overcome popf silently disregarding IF on the stack).
>
> You can regard eflags.AC as the paravirtualized eflags.IF (Xen for 
> example has a per-vcpu memory flag for the same).

Thanks Avi, I understand it now.
Andi, I will update it and resend shortly.



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