Recent commits added the explicit notion of "workaround not required" to the state of the Spectre v2 (aka. BP_HARDENING) workaround, where we just had "needed" and "unknown" before.
Export this knowledge to the rest of the kernel and enhance the existing kvm_arm_harden_branch_predictor() to report this new state as well. Export this new state to guests when they use KVM's firmware interface emulation. Signed-off-by: Andre Przywara <[email protected]> --- arch/arm/include/asm/kvm_host.h | 12 +++++++++--- arch/arm64/include/asm/cpufeature.h | 6 ++++++ arch/arm64/include/asm/kvm_host.h | 16 ++++++++++++++-- arch/arm64/kernel/cpu_errata.c | 23 ++++++++++++++++++----- virt/kvm/arm/psci.c | 10 +++++++++- 5 files changed, 56 insertions(+), 11 deletions(-) diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h index 770d73257ad9..3ae0bb6d0999 100644 --- a/arch/arm/include/asm/kvm_host.h +++ b/arch/arm/include/asm/kvm_host.h @@ -364,7 +364,11 @@ static inline void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) {} static inline void kvm_arm_vhe_guest_enter(void) {} static inline void kvm_arm_vhe_guest_exit(void) {} -static inline bool kvm_arm_harden_branch_predictor(void) +#define KVM_BP_HARDEN_UNKNOWN -1 +#define KVM_BP_HARDEN_WA_NEEDED 0 +#define KVM_BP_HARDEN_NOT_REQUIRED 1 + +static inline int kvm_arm_harden_branch_predictor(void) { switch(read_cpuid_part()) { #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR @@ -372,10 +376,12 @@ static inline bool kvm_arm_harden_branch_predictor(void) case ARM_CPU_PART_CORTEX_A12: case ARM_CPU_PART_CORTEX_A15: case ARM_CPU_PART_CORTEX_A17: - return true; + return KVM_BP_HARDEN_WA_NEEDED; #endif + case ARM_CPU_PART_CORTEX_A7: + return KVM_BP_HARDEN_NOT_REQUIRED; default: - return false; + return KVM_BP_HARDEN_UNKNOWN; } } diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 6ccdc97e5d6a..7cc58a34df43 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -622,6 +622,12 @@ static inline bool system_uses_irq_prio_masking(void) cpus_have_const_cap(ARM64_HAS_IRQ_PRIO_MASKING); } +#define ARM64_BP_HARDEN_UNKNOWN -1 +#define ARM64_BP_HARDEN_WA_NEEDED 0 +#define ARM64_BP_HARDEN_NOT_REQUIRED 1 + +int get_spectre_v2_workaround_state(void); + #define ARM64_SSBD_UNKNOWN -1 #define ARM64_SSBD_FORCE_DISABLE 0 #define ARM64_SSBD_KERNEL 1 diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a01fe087e022..b1d484d49d39 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -555,9 +555,21 @@ static inline void kvm_arm_vhe_guest_exit(void) isb(); } -static inline bool kvm_arm_harden_branch_predictor(void) +#define KVM_BP_HARDEN_UNKNOWN -1 +#define KVM_BP_HARDEN_WA_NEEDED 0 +#define KVM_BP_HARDEN_NOT_REQUIRED 1 + +static inline int kvm_arm_harden_branch_predictor(void) { - return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR); + switch (get_spectre_v2_workaround_state()) { + case ARM64_BP_HARDEN_WA_NEEDED: + return KVM_BP_HARDEN_WA_NEEDED; + case ARM64_BP_HARDEN_NOT_REQUIRED: + return KVM_BP_HARDEN_NOT_REQUIRED; + case ARM64_BP_HARDEN_UNKNOWN: + default: + return KVM_BP_HARDEN_UNKNOWN; + } } #define KVM_SSBD_UNKNOWN -1 diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 1b9ce0fdd81d..04b659674f3a 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -549,6 +549,17 @@ cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused) static bool __hardenbp_enab = true; static bool __spectrev2_safe = true; +int get_spectre_v2_workaround_state(void) +{ + if (__spectrev2_safe) + return ARM64_BP_HARDEN_NOT_REQUIRED; + + if (!__hardenbp_enab) + return ARM64_BP_HARDEN_UNKNOWN; + + return ARM64_BP_HARDEN_WA_NEEDED; +} + /* * List of CPUs that do not need any Spectre-v2 mitigation at all. */ @@ -828,13 +839,15 @@ ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) { - if (__spectrev2_safe) + switch (get_spectre_v2_workaround_state()) { + case ARM64_BP_HARDEN_NOT_REQUIRED: return sprintf(buf, "Not affected\n"); - - if (__hardenbp_enab) + case ARM64_BP_HARDEN_WA_NEEDED: return sprintf(buf, "Mitigation: Branch predictor hardening\n"); - - return sprintf(buf, "Vulnerable\n"); + case ARM64_BP_HARDEN_UNKNOWN: + default: + return sprintf(buf, "Vulnerable\n"); + } } ssize_t cpu_show_spec_store_bypass(struct device *dev, diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c index 34d08ee63747..900b67c2720f 100644 --- a/virt/kvm/arm/psci.c +++ b/virt/kvm/arm/psci.c @@ -412,8 +412,16 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) feature = smccc_get_arg1(vcpu); switch(feature) { case ARM_SMCCC_ARCH_WORKAROUND_1: - if (kvm_arm_harden_branch_predictor()) + switch (kvm_arm_harden_branch_predictor()) { + case KVM_BP_HARDEN_UNKNOWN: + break; + case KVM_BP_HARDEN_WA_NEEDED: val = SMCCC_RET_SUCCESS; + break; + case KVM_BP_HARDEN_NOT_REQUIRED: + val = SMCCC_RET_NOT_REQUIRED; + break; + } break; case ARM_SMCCC_ARCH_WORKAROUND_2: switch (kvm_arm_have_ssbd()) { -- 2.17.1 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
