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

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Date:   Thu, 14 Jan 2021 09:58:51 +0800
From:   "Xu, Like" <like.xu@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        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 2021/1/14 2:06, Peter Zijlstra wrote:
> 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

You're right, I think it should be:

     pmu->fixed_ctr_ctrl_mask &= ~(0xbull << (i * 4));

w/o invertion and I will fix it in the next version.

>
>> +	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
>>