[PATCH v1 1/2] KVM: arm64: PMU: Restore the host's PMUSERENR_EL0

[Reiji Watanabe]

Restore the host's PMUSERENR_EL0 value instead of clearing it,
before returning back to userspace, as the host's EL0 might have
a direct access to PMU registers (some bits of PMUSERENR_EL0
might not be zero).

Fixes: 83a7a4d643d3 ("arm64: perf: Enable PMU counter userspace access for perf event")
Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/include/asm/kvm_host.h       | 3 +++
 arch/arm64/kvm/hyp/include/hyp/switch.h | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bcd774d74f34..82220ecec10e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -544,6 +544,9 @@ struct kvm_vcpu_arch {
 
 	/* Per-vcpu CCSIDR override or NULL */
 	u32 *ccsidr;
+
+	/* the value of host's pmuserenr_el0 before guest entry */
+	u64	host_pmuserenr_el0;
 };
 
 /*
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 07d37ff88a3f..44b84fbdde0d 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -82,6 +82,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
 	 */
 	if (kvm_arm_support_pmu_v3()) {
 		write_sysreg(0, pmselr_el0);
+		vcpu->arch.host_pmuserenr_el0 = read_sysreg(pmuserenr_el0);
 		write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
 	}
 
@@ -106,7 +107,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
 
 	write_sysreg(0, hstr_el2);
 	if (kvm_arm_support_pmu_v3())
-		write_sysreg(0, pmuserenr_el0);
+		write_sysreg(vcpu->arch.host_pmuserenr_el0, pmuserenr_el0);
 
 	if (cpus_have_final_cap(ARM64_SME)) {
 		sysreg_clear_set_s(SYS_HFGRTR_EL2, 0,
-- 
2.40.0.348.gf938b09366-goog