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.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: oupton

arch/arm64/include/asm/cpufeature.h

@@ -838,6 +838,11 @@ static inline bool system_supports_poe(void)
 		alternative_has_cap_unlikely(ARM64_HAS_S1POE);
 }
 
+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);
 

arch/arm64/kernel/cpufeature.c

@@ -1866,6 +1866,19 @@ static bool has_lpa2(const struct arm64_cpu_capabilities *entry, int scope)
 }
 #endif
 
+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 = 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;
+}
+
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 #define KPTI_NG_TEMP_VA		(-(1UL << PMD_SHIFT))
 
@@ -2890,6 +2903,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		ARM64_CPUID_FIELDS(ID_AA64MMFR3_EL1, S1POE, IMP)
 	},
 #endif
+	{
+		.desc = "PMUv3",
+		.capability = ARM64_HAS_PMUV3,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_pmuv3,
+	},
 	{},
 };
 

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -215,7 +215,7 @@ 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);
@@ -251,7 +251,7 @@ 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);

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();

arch/arm64/tools/cpucaps

@@ -44,6 +44,7 @@ HAS_LSE_ATOMICS
 HAS_MOPS
 HAS_NESTED_VIRT
 HAS_PAN
+HAS_PMUV3
 HAS_S1PIE
 HAS_S1POE
 HAS_RAS_EXTN

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)