linux-kernel - Re: [PATCH v2] KVM: x86/pmu: Manipulate FIXED_CTR

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Message-ID: <18e606ba-d6b2-02f0-1511-d949c4c1e6ed@linux.intel.com>
Date:   Wed, 23 Aug 2023 10:22:41 +0800
From:   "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     kvm@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhang Xiong <xiong.y.zhang@...el.com>,
        Lv Zhiyuan <zhiyuan.lv@...el.com>,
        Dapeng Mi <dapeng1.mi@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v2] KVM: x86/pmu: Manipulate FIXED_CTR_CTRL MSR with
 macros

On 8/21/2023 4:05 PM, Like Xu wrote:
> On 15/8/2023 11:28 am, Dapeng Mi wrote:
>> Magic numbers are used to manipulate the bit fields of
>> FIXED_CTR_CTRL MSR. This is not read-friendly and use macros to replace
>> these magic numbers to increase the readability.
>
> More, reuse INTEL_FIXED_0_* macros for pmu->fixed_ctr_ctrl_mask, pls.

Sure. Thanks.
>
>>
>> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
>> ---
>>   arch/x86/kvm/pmu.c | 10 +++++-----
>>   arch/x86/kvm/pmu.h |  6 ++++--
>>   2 files changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
>> index edb89b51b383..fb4ef2da3e32 100644
>> --- a/arch/x86/kvm/pmu.c
>> +++ b/arch/x86/kvm/pmu.c
>> @@ -420,11 +420,11 @@ static void reprogram_counter(struct kvm_pmc *pmc)
>>       if (pmc_is_fixed(pmc)) {
>>           fixed_ctr_ctrl = fixed_ctrl_field(pmu->fixed_ctr_ctrl,
>>                             pmc->idx - INTEL_PMC_IDX_FIXED);
>> -        if (fixed_ctr_ctrl & 0x1)
>> +        if (fixed_ctr_ctrl & INTEL_FIXED_0_KERNEL)
>>               eventsel |= ARCH_PERFMON_EVENTSEL_OS;
>> -        if (fixed_ctr_ctrl & 0x2)
>> +        if (fixed_ctr_ctrl & INTEL_FIXED_0_USER)
>>               eventsel |= ARCH_PERFMON_EVENTSEL_USR;
>> -        if (fixed_ctr_ctrl & 0x8)
>> +        if (fixed_ctr_ctrl & INTEL_FIXED_0_ENABLE_PMI)
>>               eventsel |= ARCH_PERFMON_EVENTSEL_INT;
>>           new_config = (u64)fixed_ctr_ctrl;
>>       }
>> @@ -749,8 +749,8 @@ static inline bool cpl_is_matched(struct kvm_pmc 
>> *pmc)
>>       } else {
>>           config = fixed_ctrl_field(pmc_to_pmu(pmc)->fixed_ctr_ctrl,
>>                         pmc->idx - INTEL_PMC_IDX_FIXED);
>> -        select_os = config & 0x1;
>> -        select_user = config & 0x2;
>> +        select_os = config & INTEL_FIXED_0_KERNEL;
>> +        select_user = config & INTEL_FIXED_0_USER;
>>       }
>>         return (static_call(kvm_x86_get_cpl)(pmc->vcpu) == 0) ? 
>> select_os : select_user;
>> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
>> index 7d9ba301c090..ffda2ecc3a22 100644
>> --- a/arch/x86/kvm/pmu.h
>> +++ b/arch/x86/kvm/pmu.h
>> @@ -12,7 +12,8 @@
>>                         MSR_IA32_MISC_ENABLE_BTS_UNAVAIL)
>>     /* retrieve the 4 bits for EN and PMI out of IA32_FIXED_CTR_CTRL */
>> -#define fixed_ctrl_field(ctrl_reg, idx) (((ctrl_reg) >> ((idx)*4)) & 
>> 0xf)
>> +#define fixed_ctrl_field(ctrl_reg, idx) \
>> +    (((ctrl_reg) >> ((idx) * INTEL_FIXED_BITS_STRIDE)) & 
>> INTEL_FIXED_BITS_MASK)
>>     #define VMWARE_BACKDOOR_PMC_HOST_TSC        0x10000
>>   #define VMWARE_BACKDOOR_PMC_REAL_TIME        0x10001
>> @@ -165,7 +166,8 @@ static inline bool pmc_speculative_in_use(struct 
>> kvm_pmc *pmc)
>>         if (pmc_is_fixed(pmc))
>>           return fixed_ctrl_field(pmu->fixed_ctr_ctrl,
>> -                    pmc->idx - INTEL_PMC_IDX_FIXED) & 0x3;
>> +                    pmc->idx - INTEL_PMC_IDX_FIXED) &
>> +                    (INTEL_FIXED_0_KERNEL | INTEL_FIXED_0_USER);
>>         return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE;
>>   }
>>
>> base-commit: 240f736891887939571854bd6d734b6c9291f22e