Re: [PATCH] Introduce bitmask for apic attention reasons.

[Gleb Natapov <gleb@redhat.com>]

On Thu, Apr 19, 2012 at 12:53:12PM +0300, Avi Kivity wrote:
> On 04/19/2012 12:33 PM, Gleb Natapov wrote:
> > The patch introduces a bitmap that will hold reasons apic should be
> > checked during vmexit. This is in a preparation for vp eoi patch
> > that will add one more check on vmexit. With the bitmap we can do
> > if(apic_attention) to check everything simultaneously which will
> > add zero overhead on the fast path.
> >
> 
> Good idea.
> 
> >  
> > +#define KVM_APIC_CHECK_VAPIC	0
> 
> Comment above relating this to apic_attention.
> 
OK.

> >  	vcpu->arch.apic->vapic_addr = vapic_addr;
> > +	if (vapic_addr)
> > +		__set_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention);
> > +	else
> > +		__clear_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention);
> >  }
> >
> 
> Unrelated: this pattern is probably common.  Would be nice to have a
> __deposit_bit() function.
> 
What semantics should it have? Set bit A in bitmap B if value C is
non-zero?

--
			Gleb.