@@ -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;
}
}
@@ -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
@@ -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
@@ -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,
@@ -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()) {
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 <andre.przywara@arm.com> --- 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(-)