Re: [PATCH v2 13/16] KVM: x86/pmu: Factor out fixed counter control bit calculation

[Mi, Dapeng]

Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>


On 8/28/2026 6:37 AM, Zide Chen wrote:
> Rename intel_pmu_enable_fixed_counter_bits() to
> intel_pmu_fixed_ctrl_bits() and have it return the computed fixed
> counter control mask instead of updating fixed_ctr_ctrl_rsvd directly.
>
> Accumulate the desired fixed counter control bits during PMU setup and
> apply them once in intel_pmu_refresh().
>
> Move the helper next to intel_pmu_set_msr() so it can also be reused
> there, which will be needed for upcoming ANYTHREAD_DEPRECATION
> emulation.
>
> No functional change intended.
>
> Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
> ---
> v2: New patch
> ---
>  arch/x86/kvm/vmx/pmu_intel.c | 32 +++++++++++++++++++-------------
>  1 file changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 1ce69e764ae1..c7472778137a 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -421,6 +421,18 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	return 0;
>  }
>  
> +static u64 intel_pmu_fixed_ctrl_bits(struct kvm_pmu *pmu, u64 bits)
> +{
> +	unsigned long fixed_mask = kvm_fixed_pmc_mask(pmu);
> +	u64 fixed_ctrl_bits = 0;
> +	int i;
> +
> +	kvm_for_each_fixed_counter(i, fixed_mask)
> +		fixed_ctrl_bits |= intel_fixed_bits_by_idx(i, bits);
> +
> +	return fixed_ctrl_bits;
> +}
> +
>  static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  {
>  	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
> @@ -533,20 +545,12 @@ static __always_inline u64 intel_get_fixed_pmc_eventsel(unsigned int index)
>  	return eventsel;
>  }
>  
> -static void intel_pmu_enable_fixed_counter_bits(struct kvm_pmu *pmu, u64 bits)
> -{
> -	unsigned long fixed_mask = kvm_fixed_pmc_mask(pmu);
> -	int i;
> -
> -	kvm_for_each_fixed_counter(i, fixed_mask)
> -		pmu->fixed_ctr_ctrl_rsvd &= ~intel_fixed_bits_by_idx(i, bits);
> -}
> -
>  static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
>  	struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
>  	struct kvm_cpuid_entry2 *entry;
> +	u64 fixed_enable_bits = 0;
>  	union cpuid10_eax eax;
>  	union cpuid10_edx edx;
>  	u64 perf_capabilities;
> @@ -625,9 +629,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>  					  kvm_pmu_cap.bit_width_fixed);
>  	pmu->counter_bitmask[KVM_PMC_FIXED] = BIT_ULL(edx.split.bit_width_fixed) - 1;
>  
> -	intel_pmu_enable_fixed_counter_bits(pmu, INTEL_FIXED_0_KERNEL |
> -						 INTEL_FIXED_0_USER |
> -						 INTEL_FIXED_0_ENABLE_PMI);
> +	fixed_enable_bits |= INTEL_FIXED_0_KERNEL | INTEL_FIXED_0_USER |
> +			     INTEL_FIXED_0_ENABLE_PMI;
>  
>  	counter_rsvd = ~(kvm_gp_pmc_mask(pmu) |
>  			((u64)kvm_fixed_pmc_mask(pmu) << KVM_FIXED_PMC_BASE_IDX));
> @@ -651,11 +654,14 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
>  			pmu->pebs_enable_rsvd = counter_rsvd;
>  			pmu->eventsel_rsvd &= ~ICL_EVENTSEL_ADAPTIVE;
>  			pmu->pebs_data_cfg_rsvd = ~0xff00000full;
> -			intel_pmu_enable_fixed_counter_bits(pmu, ICL_FIXED_0_ADAPTIVE);
> +			fixed_enable_bits |= ICL_FIXED_0_ADAPTIVE;
>  		} else {
>  			pmu->pebs_enable_rsvd = ~kvm_gp_pmc_mask(pmu);
>  		}
>  	}
> +
> +	pmu->fixed_ctr_ctrl_rsvd &=
> +		~intel_pmu_fixed_ctrl_bits(pmu, fixed_enable_bits);
>  }
>  
>  static void intel_pmu_init(struct kvm_vcpu *vcpu)