Re: [PATCH 7/9] KVM: Expose the architectural performance monitoring CPUID leaf

[David Ahern <dsahern@gmail.com>]

On 10/30/2011 10:53 AM, Gleb Natapov wrote:
> From: Avi Kivity <avi@redhat.com>
> 
> Provide a CPUID leaf that describes the emulated PMU.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> ---
>  arch/x86/kvm/x86.c |   23 ++++++++++++++++++++++-
>  1 files changed, 22 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5ea4cb8..56153a9 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2543,6 +2543,28 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  	}
>  	case 9:
>  		break;
> +	case 0xa: { /* Architectural Performance Monitoring */
> +		struct x86_pmu_capability cap;
> +
> +		perf_get_x86_pmu_capability(&cap);
> +
> +		/*
> +		 * Only support guest architectural pmu on a host
> +		 * with architectural pmu.
> +		 */
> +		if (!cap.version)
> +			memset(&cap, 0, sizeof(cap));
> +
> +		entry->eax = min(cap.version, 2)
> +			| (cap.num_counters_gp << 8)
> +			| (cap.bit_width_gp << 16)
> +			| (cap.events_mask_len << 24);
> +		entry->ebx = cap.events_mask;
> +		entry->ecx = 0;
> +		entry->edx = cap.num_counters_fixed
> +			| (cap.bit_width_fixed << 5);
> +		break;
> +	}

If PERF_EVENTS is disabled in the host kernel will KVM return the right
thing for the guest that might have PERF_EVENTS enabled?

David


>  	/* function 0xb has additional index. */
>  	case 0xb: {
>  		int i, level_type;
> @@ -2637,7 +2659,6 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  	case 3: /* Processor serial number */
>  	case 5: /* MONITOR/MWAIT */
>  	case 6: /* Thermal management */
> -	case 0xA: /* Architectural Performance Monitoring */
>  	case 0x80000007: /* Advanced power management */
>  	case 0xC0000002:
>  	case 0xC0000003: