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(-)
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>