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authorAndre Przywara <andre.przywara@arm.com>2019-05-03 15:27:48 +0100
committerMarc Zyngier <marc.zyngier@arm.com>2019-07-05 13:56:27 +0100
commitc118bbb52743df70e6297671606c1c08edc659fe (patch)
tree3058edcfc6f08fa7b68f9e5ff037c9dc219255a6
parent80f393a23be68e2f8a0f74258d6155438c200bbd (diff)
arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests
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> Reviewed-by: Steven Price <steven.price@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
-rw-r--r--arch/arm/include/asm/kvm_host.h12
-rw-r--r--arch/arm64/include/asm/cpufeature.h6
-rw-r--r--arch/arm64/include/asm/kvm_host.h16
-rw-r--r--arch/arm64/kernel/cpu_errata.c23
-rw-r--r--virt/kvm/arm/psci.c10
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 f80418ddeb60..e74e8f408987 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -362,7 +362,11 @@ static inline void kvm_vcpu_pmu_restore_host(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
@@ -370,10 +374,12 @@ 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 373799b7982f..948427f6b3d9 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -614,6 +614,12 @@ 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 c328191aa202..d9770daf3d7d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -620,9 +620,21 @@ 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 ca11ff7bf55e..1e43ba5c79b7 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -554,6 +554,17 @@ 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.
*/
@@ -854,13 +865,15 @@ 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 be3c9cdca9f3..355b9e38a42d 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -401,8 +401,16 @@ 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()) {

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