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

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Message-ID: <305fa208-e1d6-7e22-3156-11fd551a8dd1@gmail.com>
Date:   Mon, 21 Aug 2023 16:05:32 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Dapeng Mi <dapeng1.mi@...ux.intel.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 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.

> 
> 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