KVM: arm64: Use a cpucap to determine if system supports FEAT_PMUv3

KVM is about to learn some new tricks to virtualize PMUv3 on IMPDEF
hardware. As part of that, we now need to differentiate host support
from guest support for PMUv3.

Add a cpucap to determine if an architectural PMUv3 is present to guard
host usage of PMUv3 controls.

Tested-by: Janne Grunau <j@jannau.net>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250305202641.428114-6-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 0b5ca6e0eb0932f90eeb8db1971849102dcdafd7..9d769291a3067b248ca012a996e4d684d0929afc 100644 (file)
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -71,6 +71,8 @@ cpucap_is_possible(const unsigned int cap)
                 * KVM MPAM support doesn't rely on the host kernel supporting MPAM.
                */
                return true;
+       case ARM64_HAS_PMUV3:
+               return IS_ENABLED(CONFIG_HW_PERF_EVENTS);
        }
 
        return true;

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index e0e4478f5fb52d76f2ab4cab914d9111ce03b7a1..0eff048848b84ce62aa391c7dc8cc0b0a73ac35a 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -866,6 +866,11 @@ static __always_inline bool system_supports_mpam_hcr(void)
        return alternative_has_cap_unlikely(ARM64_MPAM_HCR);
 }
 
+static inline bool system_supports_pmuv3(void)
+{
+       return cpus_have_final_cap(ARM64_HAS_PMUV3);
+}
+
 int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
 bool try_emulate_mrs(struct pt_regs *regs, u32 isn);
 

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d561cf3b8ac7b11784282dc889852ef52a7b8f6e..adb26697d908ce2c544a08a980811a726e217484 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1898,6 +1898,28 @@ static bool has_lpa2(const struct arm64_cpu_capabilities *entry, int scope)
 }
 #endif
 
+#ifdef CONFIG_HW_PERF_EVENTS
+static bool has_pmuv3(const struct arm64_cpu_capabilities *entry, int scope)
+{
+       u64 dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
+       unsigned int pmuver;
+
+       /*
+        * PMUVer follows the standard ID scheme for an unsigned field with the
+        * exception of 0xF (IMP_DEF) which is treated specially and implies
+        * FEAT_PMUv3 is not implemented.
+        *
+        * See DDI0487L.a D24.1.3.2 for more details.
+        */
+       pmuver = cpuid_feature_extract_unsigned_field(dfr0,
+                                                     ID_AA64DFR0_EL1_PMUVer_SHIFT);
+       if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
+               return false;
+
+       return pmuver >= ID_AA64DFR0_EL1_PMUVer_IMP;
+}
+#endif
+
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 #define KPTI_NG_TEMP_VA                (-(1UL << PMD_SHIFT))
 
@@ -2998,6 +3020,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
                .matches = has_cpuid_feature,
                ARM64_CPUID_FIELDS(ID_AA64PFR1_EL1, GCS, IMP)
        },
+#endif
+#ifdef CONFIG_HW_PERF_EVENTS
+       {
+               .desc = "PMUv3",
+               .capability = ARM64_HAS_PMUV3,
+               .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+               .matches = has_pmuv3,
+       },
 #endif
        {},
 };

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 23bbe28eaaf95d2a61b6c189d603c23a85f71203..b741ea6aefa58f5dabf02aeb7f9bd8029db151be 100644 (file)
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -244,7 +244,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
         * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
         * EL1 instead of being trapped to EL2.
         */
-       if (kvm_arm_support_pmu_v3()) {
+       if (system_supports_pmuv3()) {
                struct kvm_cpu_context *hctxt;
 
                write_sysreg(0, pmselr_el0);
@@ -281,7 +281,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
        write_sysreg(*host_data_ptr(host_debug_state.mdcr_el2), mdcr_el2);
 
        write_sysreg(0, hstr_el2);
-       if (kvm_arm_support_pmu_v3()) {
+       if (system_supports_pmuv3()) {
                struct kvm_cpu_context *hctxt;
 
                hctxt = host_data_ptr(host_ctxt);

diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 0b3adf3e17b49e48c775fe092503064e26a97358..6b48a3d16d0d5e1dea2d956bb2794c31ba38ae00 100644 (file)
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -41,7 +41,7 @@ void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr)
 {
        struct kvm_pmu_events *pmu = kvm_get_pmu_events();
 
-       if (!kvm_arm_support_pmu_v3() || !kvm_pmu_switch_needed(attr))
+       if (!system_supports_pmuv3() || !kvm_pmu_switch_needed(attr))
                return;
 
        if (!attr->exclude_host)
@@ -57,7 +57,7 @@ void kvm_clr_pmu_events(u64 clr)
 {
        struct kvm_pmu_events *pmu = kvm_get_pmu_events();
 
-       if (!kvm_arm_support_pmu_v3())
+       if (!system_supports_pmuv3())
                return;
 
        pmu->events_host &= ~clr;
@@ -133,7 +133,7 @@ void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu)
        struct kvm_pmu_events *pmu;
        u64 events_guest, events_host;
 
-       if (!kvm_arm_support_pmu_v3() || !has_vhe())
+       if (!system_supports_pmuv3() || !has_vhe())
                return;
 
        preempt_disable();
@@ -154,7 +154,7 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu)
        struct kvm_pmu_events *pmu;
        u64 events_guest, events_host;
 
-       if (!kvm_arm_support_pmu_v3() || !has_vhe())
+       if (!system_supports_pmuv3() || !has_vhe())
                return;
 
        pmu = kvm_get_pmu_events();
@@ -180,7 +180,7 @@ bool kvm_set_pmuserenr(u64 val)
        struct kvm_cpu_context *hctxt;
        struct kvm_vcpu *vcpu;
 
-       if (!kvm_arm_support_pmu_v3() || !has_vhe())
+       if (!system_supports_pmuv3() || !has_vhe())
                return false;
 
        vcpu = kvm_get_running_vcpu();

diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 1e65f2fb45bd17fc994dca7612ebcb1178bce60b..ee4316cb36905f993828ca1333f1c5c2b3c39cba 100644 (file)
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -45,6 +45,7 @@ HAS_LSE_ATOMICS
 HAS_MOPS
 HAS_NESTED_VIRT
 HAS_PAN
+HAS_PMUV3
 HAS_S1PIE
 HAS_S1POE
 HAS_RAS_EXTN

diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 147bd3ee4f7bae1089a4df4e201a1bc4cbad3b57..3a8edd78240f72c920420f8ae0d8d58a0256655a 100644 (file)
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -86,7 +86,7 @@ void kvm_vcpu_pmu_resync_el0(void);
  */
 #define kvm_pmu_update_vcpu_events(vcpu)                               \
        do {                                                            \
-               if (!has_vhe() && kvm_arm_support_pmu_v3())             \
+               if (!has_vhe() && system_supports_pmuv3())              \
                        vcpu->arch.pmu.events = *kvm_get_pmu_events();  \
        } while (0)