KVM: arm64: Don't access PMSELR_EL0/PMUSERENR_EL0 when no PMU is available

When running under a nesting hypervisor, it isn't guaranteed that
the virtual HW will include a PMU. In which case, let's not try
to access the PMU registers in the world switch, as that'd be
deadly.

Reported-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210209114844.3278746-3-maz@kernel.org
Message-Id: <20210305185254.3730990-6-maz@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 23f1a557bd9f04fb61c90d2428fcc12ecca127ac..5aa9ed1e9ec6189af9beede0488e9e982044da0d 100644 (file)
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -101,6 +101,9 @@ KVM_NVHE_ALIAS(__stop___kvm_ex_table);
 /* Array containing bases of nVHE per-CPU memory regions. */
 KVM_NVHE_ALIAS(kvm_arm_hyp_percpu_base);
 
+/* PMU available static key */
+KVM_NVHE_ALIAS(kvm_arm_pmu_available);
+
 #endif /* CONFIG_KVM */
 
 #endif /* __ARM64_KERNEL_IMAGE_VARS_H */

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 54f4860cd87c06b1ed701eb3f2664176b6458806..6c1f51f25eb340154247b6381b6b482e1c76ccd4 100644 (file)
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -90,15 +90,18 @@ 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.
         */
-       write_sysreg(0, pmselr_el0);
-       write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
+       if (kvm_arm_support_pmu_v3()) {
+               write_sysreg(0, pmselr_el0);
+               write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
+       }
        write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
 }
 
 static inline void __deactivate_traps_common(void)
 {
        write_sysreg(0, hstr_el2);
-       write_sysreg(0, pmuserenr_el0);
+       if (kvm_arm_support_pmu_v3())
+               write_sysreg(0, pmuserenr_el0);
 }
 
 static inline void ___activate_traps(struct kvm_vcpu *vcpu)