[PATCH v4.4 37/45] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support

From: Viresh Kumar <viresh.kumar@linaro.org>
To: linux-arm-kernel@lists.infradead.org,
	Julien Thierry <Julien.Thierry@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	stable@vger.kernel.org, mark.brown@arm.com,
	Catalin Marinas <catalin.marinas@arm.com>,
	Russell King <rmk+kernel@arm.linux.org.uk>
Subject: [PATCH v4.4 37/45] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support
Date: Fri, 14 Jun 2019 08:38:20 +0530	[thread overview]
Message-ID: <e79f92083760ecd32cd521e29a3d9d3227737ff2.1560480942.git.viresh.kumar@linaro.org> (raw)
In-Reply-To: <cover.1560480942.git.viresh.kumar@linaro.org>

From: Mark Rutland <mark.rutland@arm.com>

commit 6167ec5c9145cdf493722dfd80a5d48bafc4a18a upstream.

A new feature of SMCCC 1.1 is that it offers firmware-based CPU
workarounds. In particular, SMCCC_ARCH_WORKAROUND_1 provides
BP hardening for CVE-2017-5715.

If the host has some mitigation for this issue, report that
we deal with it using SMCCC_ARCH_WORKAROUND_1, as we apply the
host workaround on every guest exit.

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ v4.4: account for files moved to virt/ upstream ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 arch/arm/include/asm/kvm_host.h   | 6 ++++++
 arch/arm/kvm/psci.c               | 9 ++++++++-
 arch/arm64/include/asm/kvm_host.h | 5 +++++
 include/linux/arm-smccc.h         | 5 +++++
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 6692982c9b57..2009894d9a8a 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -237,4 +237,10 @@ static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
 
+static inline bool kvm_arm_harden_branch_predictor(void)
+{
+	/* No way to detect it yet, pretend it is not there. */
+	return false;
+}
+
 #endif /* __ARM_KVM_HOST_H__ */
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index 9abf40734723..747319490268 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -403,13 +403,20 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 {
 	u32 func_id = smccc_get_function(vcpu);
 	u32 val = PSCI_RET_NOT_SUPPORTED;
+	u32 feature;
 
 	switch (func_id) {
 	case ARM_SMCCC_VERSION_FUNC_ID:
 		val = ARM_SMCCC_VERSION_1_1;
 		break;
 	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
-		/* Nothing supported yet */
+		feature = smccc_get_arg1(vcpu);
+		switch(feature) {
+		case ARM_SMCCC_ARCH_WORKAROUND_1:
+			if (kvm_arm_harden_branch_predictor())
+				val = 0;
+			break;
+		}
 		break;
 	default:
 		return kvm_psci_call(vcpu);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a35ce7266aac..aca3a7e28777 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -258,4 +258,9 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
 
+static inline bool kvm_arm_harden_branch_predictor(void)
+{
+	return cpus_have_cap(ARM64_HARDEN_BRANCH_PREDICTOR);
+}
+
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index da9f3916f9a9..1f02e4045a9e 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -73,6 +73,11 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 1)
 
+#define ARM_SMCCC_ARCH_WORKAROUND_1					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_32,				\
+			   0, 0x8000)
+
 #ifndef __ASSEMBLY__
 
 /**
-- 
2.21.0.rc0.269.g1a574e7a288b


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