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

[Avi Kivity <avi@redhat.com>]

On 10/30/2011 06:53 PM, 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);

What if num_counters_gp is larger than our array?

> +		entry->ebx = cap.events_mask;
> +		entry->ecx = 0;
> +		entry->edx = cap.num_counters_fixed
> +			| (cap.bit_width_fixed << 5);

Ditto.



-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.