Re: [PATCH RESEND] KVM: x86/pmu: Make top-down.slots event unavailable in supported leaf

[Paolo Bonzini <pbonzini@redhat.com>]

On 1/5/22 06:07, Like Xu wrote:
> +		/*
> +		 * The 8th Intel pre-defined architectural event (Topdown Slots) will be supported
> +		 * if the 4th fixed counter exists && EAX[31:24] > 7 && EBX[7] = 0.
> +		 *
> +		 * Currently, KVM needs to set EAX[31:24] < 8 or EBX[7] == 1
> +		 * to make this event unavailable in a consistent way.
> +		 */
> +		if (edx.split.num_counters_fixed < 4) {
> +			if (eax.split.mask_length > 7)
> +				eax.split.mask_length--;
> +			if (eax.split.mask_length > 7)
> +				cap.events_mask |= BIT_ULL(7);
> +		}
> +

The first "> 7" is wrong; it should be == 8, shouldn't it?  Something like

if (edx.split.num_counters_fixed < 4 && eax.split.mask_length >= 8) {
	if (eax.split.mask_length == 8)
		eax.split.mask_length--;
	else
		cap.events_mask |= BIT_ULL(7);
}

is what you mean, I think?

Paolo