linux-kernel - Re: [PATCH v3 03/17] KVM: x86/pmu: Introduce the ctrl

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Date:   Wed, 13 Jan 2021 19:06:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, eranian@...gle.com,
        kvm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <andi@...stfloor.org>,
        Kan Liang <kan.liang@...ux.intel.com>, wei.w.wang@...el.com,
        luwei.kang@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/17] KVM: x86/pmu: Introduce the ctrl_mask value for
 fixed counter

On Mon, Jan 04, 2021 at 09:15:28PM +0800, Like Xu wrote:
> @@ -327,6 +328,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>  	pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
>  	pmu->version = 0;
>  	pmu->reserved_bits = 0xffffffff00200000ull;
> +	pmu->fixed_ctr_ctrl_mask = ~0ull;

All 1s

>  
>  	entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
>  	if (!entry)
> @@ -358,6 +360,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>  			((u64)1 << edx.split.bit_width_fixed) - 1;
>  	}
>  
> +	for (i = 0; i < pmu->nr_arch_fixed_counters; i++)
> +		pmu->fixed_ctr_ctrl_mask |= (0xbull << (i * 4));

With some extra 1s on top

> +	pmu->fixed_ctr_ctrl_mask = ~pmu->fixed_ctr_ctrl_mask;

Inverted is all 0s, always.

>  	pmu->global_ctrl = ((1ull << pmu->nr_arch_gp_counters) - 1) |
>  		(((1ull << pmu->nr_arch_fixed_counters) - 1) << INTEL_PMC_IDX_FIXED);
>  	pmu->global_ctrl_mask = ~pmu->global_ctrl;
> -- 
> 2.29.2
>