4.15-stable review patch. If anyone has any objections, please let me know.
------------------ From: Marc Zyngier <[email protected]> Commit 6167ec5c9145 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 <[email protected]> Reviewed-by: Christoffer Dall <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Signed-off-by: Catalin Marinas <[email protected]> Signed-off-by: Will Deacon <[email protected]> Conflicts: arch/arm/include/asm/kvm_host.h arch/arm64/include/asm/kvm_host.h Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm/include/asm/kvm_host.h | 6 ++++++ arch/arm64/include/asm/kvm_host.h | 5 +++++ include/linux/arm-smccc.h | 5 +++++ virt/kvm/arm/psci.c | 9 ++++++++- 4 files changed, 24 insertions(+), 1 deletion(-) --- a/arch/arm/include/asm/kvm_host.h +++ b/arch/arm/include/asm/kvm_host.h @@ -301,4 +301,10 @@ int kvm_arm_vcpu_arch_has_attr(struct kv /* All host FP/SIMD state is restored on guest exit, so nothing to save: */ static inline void kvm_fpsimd_flush_cpu_state(void) {} +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__ */ --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -396,4 +396,9 @@ static inline void kvm_fpsimd_flush_cpu_ sve_flush_cpu_state(); } +static inline bool kvm_arm_harden_branch_predictor(void) +{ + return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR); +} + #endif /* __ARM64_KVM_HOST_H__ */ --- 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> --- a/virt/kvm/arm/psci.c +++ b/virt/kvm/arm/psci.c @@ -405,13 +405,20 @@ int kvm_hvc_call_handler(struct kvm_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);
