[v4.9.y,35/42] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support

Message ID 20180412111138.40990-36-mark.rutland@arm.com
State New
Headers show
Series
  • arm64 spectre patches
Related show

Commit Message

Mark Rutland April 12, 2018, 11:11 a.m.
From: Marc Zyngier <marc.zyngier@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>

[v4.9: account for files moved to virt/ upstream]
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]

---
 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(-)

-- 
2.11.0

Patch

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index d5423ab15ed5..9fe1043e72d2 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -318,4 +318,10 @@  static inline int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 	return -ENXIO;
 }
 
+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 1120ad0bd3d2..3d962257c166 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 e5050388e062..37d56e85036e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -393,4 +393,9 @@  static inline void __cpu_init_stage2(void)
 		  "PARange is %d bits, unsupported configuration!", parange);
 }
 
+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 dc68aa5a7261..e1ef944ef1da 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__
 
 #include <linux/linkage.h>