Re: [PATCH 5/8] KVM: use jump label to optimize checking for HW enabled APIC in APIC_BASE MSR.

[Avi Kivity <avi@redhat.com>]

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.

> +
>  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))




-- 
error compiling committee.c: too many arguments to function