linux-kernel - [RFC PATCH v4 17/39] KVM: arm64: Set the VCPU SPE feature bit when SPE is available

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Message-Id: <20210825161815.266051-18-alexandru.elisei@arm.com>
Date:   Wed, 25 Aug 2021 17:17:53 +0100
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        will@...nel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 17/39] KVM: arm64: Set the VCPU SPE feature bit when SPE is available

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@....com>
---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/kvm/reset.c            | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1f3b46a6df81..948adb152104 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -807,6 +807,9 @@ 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/kvm/reset.c b/arch/arm64/kvm/reset.c
index cba7872d69a8..17b9f1b29c24 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 */
@@ -189,6 +190,21 @@ static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
 	return true;
 }
 
+static int kvm_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;
+}
+
 /**
  * kvm_reset_vcpu - sets core registers and sys_regs to reset value
  * @vcpu: The VCPU pointer
@@ -245,6 +261,13 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
+	if (kvm_vcpu_has_spe(vcpu)) {
+		if (kvm_vcpu_enable_spe(vcpu)) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
 	switch (vcpu->arch.target) {
 	default:
 		if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
-- 
2.33.0