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arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests

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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>
This commit is contained in:
Andre Przywara 2019-05-03 15:27:48 +01:00 committed by Marc Zyngier
parent 80f393a23b
commit c118bbb527
5 changed files with 56 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
arch/arm/include/asm/kvm_host.h
View File

@ -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;
}
}

6
arch/arm64/include/asm/cpufeature.h
View File

@ -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

16
arch/arm64/include/asm/kvm_host.h
View File

@ -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

23
arch/arm64/kernel/cpu_errata.c
View File

@ -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,

10
virt/kvm/arm/psci.c
View File

@ -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()) {