[RFC PATCH v5 17/38] KVM: arm64: Allow userspace to set the SPE feature only if SPE is present

[Alexandru Elisei]

Check that KVM SPE emulation is supported before allowing userspace to set
the KVM_ARM_VCPU_SPE feature.

According to ARM DDI 0487G.a, page D9-2946 the Profiling Buffer is disabled
if the owning Exception level is 32 bit, reject the SPE feature if the
VCPU's execution state at EL1 is aarch32.

Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/include/asm/kvm_spe.h  |  7 +++++++
 arch/arm64/kvm/reset.c            |  8 ++++++++
 arch/arm64/kvm/spe.c              | 16 ++++++++++++++++
 4 files changed, 34 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 0ebdef158020..8b3faed48914 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -815,6 +815,9 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
 
+#define kvm_vcpu_has_spe(vcpu)					\
+	(test_bit(KVM_ARM_VCPU_SPE, (vcpu)->arch.features))
+
 int kvm_trng_call(struct kvm_vcpu *vcpu);
 #ifdef CONFIG_KVM
 extern phys_addr_t hyp_mem_base;
diff --git a/arch/arm64/include/asm/kvm_spe.h b/arch/arm64/include/asm/kvm_spe.h
index 8f8b7dd7fd90..d33a46a74f78 100644
--- a/arch/arm64/include/asm/kvm_spe.h
+++ b/arch/arm64/include/asm/kvm_spe.h
@@ -13,8 +13,15 @@ static __always_inline bool kvm_supports_spe(void)
 {
 	return static_branch_likely(&kvm_spe_available);
 }
+
+int kvm_spe_vcpu_enable_spe(struct kvm_vcpu *vcpu);
 #else
 #define kvm_supports_spe()	(false)
+
+static inline int kvm_spe_vcpu_enable_spe(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
 #endif /* CONFIG_KVM_ARM_SPE */
 
 #endif /* __ARM64_KVM_SPE_H__ */
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 426bd7fbc3fd..8198156978bc 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -27,6 +27,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_spe.h>
 #include <asm/virt.h>
 
 /* Maximum phys_shift supported for any VM on this host */
@@ -251,6 +252,13 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
+	if (kvm_vcpu_has_spe(vcpu)) {
+		if (kvm_spe_vcpu_enable_spe(vcpu)) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
 	switch (vcpu->arch.target) {
 	default:
 		if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
diff --git a/arch/arm64/kvm/spe.c b/arch/arm64/kvm/spe.c
index 6cd0e24ddeec..7c6f94358cc1 100644
--- a/arch/arm64/kvm/spe.c
+++ b/arch/arm64/kvm/spe.c
@@ -7,6 +7,7 @@
 #include <linux/kvm_host.h>
 #include <linux/perf/arm_spe_pmu.h>
 
+#include <asm/kvm_emulate.h>
 #include <asm/kvm_spe.h>
 
 DEFINE_STATIC_KEY_FALSE(kvm_spe_available);
@@ -26,3 +27,18 @@ void kvm_host_spe_init(struct arm_spe_pmu *spe_pmu)
 
 	mutex_unlock(&supported_cpus_lock);
 }
+
+int kvm_spe_vcpu_enable_spe(struct kvm_vcpu *vcpu)
+{
+	if (!kvm_supports_spe())
+		return -EINVAL;
+
+	/*
+	 * The Profiling Buffer is disabled if the owning Exception level is
+	 * aarch32.
+	 */
+	if (vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT))
+		return -EINVAL;
+
+	return 0;
+}
-- 
2.33.1