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

From: Zide Chen

Date: Thu Aug 27 2026 - 18:53:13 EST


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)
--
2.55.0