From: Mark Rutland <mark.rutland@xxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
[ v4.4: account for files moved to virt/ upstream ]
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
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
