From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 5/8] KVM: use jump label to optimize checking for HW
 enabled APIC in APIC_BASE MSR.
Date: Sun, 5 Aug 2012 17:42:23 +0300
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To: Avi Kivity <avi@redhat.com>
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On Sun, Aug 05, 2012 at 05:35:21PM +0300, Avi Kivity wrote:
> On 08/05/2012 03:58 PM, Gleb Natapov wrote:
> > Usually all APICs are HW enabled so the check can be optimized out.
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > ---
> >  arch/x86/kvm/lapic.c |   29 ++++++++++++++++++++++++++++-
> >  arch/x86/kvm/lapic.h |    1 +
> >  arch/x86/kvm/x86.c   |    1 +
> >  3 files changed, 30 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index c3f14fe..1aa5528 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -34,6 +34,7 @@
> >  #include <asm/current.h>
> >  #include <asm/apicdef.h>
> >  #include <linux/atomic.h>
> > +#include <linux/jump_label.h>
> >  #include "kvm_cache_regs.h"
> >  #include "irq.h"
> >  #include "trace.h"
> > @@ -117,9 +118,13 @@ static inline int __apic_test_and_clear_vector(int vec, void *bitmap)
> >  	return __test_and_clear_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
> >  }
> >  
> > +struct static_key_deferred apic_hw_disabled __read_mostly;
> 
> On top of file please.  Add all_ to the name to make it clear we're
> talking about all apics.
> 
This is count of disabled apics really. So I think all_apic_hw_disabled
is misleading.

> > +
> >  static inline int apic_hw_enabled(struct kvm_lapic *apic)
> >  {
> > -	return (apic)->vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE;
> > +	if (static_key_false(&apic_hw_disabled.key))
> > +		return apic->vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE;
> 
> Hm, for the test to be readable, it needs to be
> 
>    if (static_key_false(&all_apics_hw_enabled))
> 
Exactly. all_ makes it so because apic_hw_disabled is a counter that
counts disabled apics. So may be call it global_hw_disabled_apic_counter?

--
			Gleb.