KVM implements the firmware interface for mitigating cache speculation
vulnerabilities. Guests may use this interface to ensure mitigation is
active.
If we want to migrate such a guest to a host with a different support
level for those workarounds, migration might need to fail, to ensure that
critical guests don't loose their protection.
Introduce a way for userland to save and restore the workarounds state.
On restoring we do checks that make sure we don't downgrade our
mitigation level.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
arch/arm/include/asm/kvm_emulate.h | 10 ++
arch/arm/include/uapi/asm/kvm.h | 12 +++
arch/arm64/include/asm/kvm_emulate.h | 14 +++
arch/arm64/include/uapi/asm/kvm.h | 10 ++
virt/kvm/arm/psci.c | 139 ++++++++++++++++++++++++---
5 files changed, 170 insertions(+), 15 deletions(-)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
index 8927cae7c966..663a02d7e6f4 100644
--- a/arch/arm/include/asm/kvm_emulate.h
+++ b/arch/arm/include/asm/kvm_emulate.h
@@ -283,6 +283,16 @@ static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
return vcpu_cp15(vcpu, c0_MPIDR) & MPIDR_HWID_BITMASK;
}
+static inline bool kvm_arm_get_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+
+static inline void kvm_arm_set_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu,
+ bool flag)
+{
+}
+
static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
{
*vcpu_cpsr(vcpu) |= PSR_E_BIT;
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index 4602464ebdfb..dfce6fdbd03b 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -214,6 +214,18 @@ struct kvm_vcpu_events {
#define KVM_REG_ARM_FW_REG(r) (KVM_REG_ARM | KVM_REG_SIZE_U64 | \
KVM_REG_ARM_FW | ((r) & 0xffff))
#define KVM_REG_ARM_PSCI_VERSION KVM_REG_ARM_FW_REG(0)
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1 KVM_REG_ARM_FW_REG(1)
+ /* Higher values mean better protection. */
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL 0
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL 1
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_UNAFFECTED 2
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2 KVM_REG_ARM_FW_REG(2)
+ /* Higher values mean better protection. */
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL 0
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN 1
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL 2
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNAFFECTED 3
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED (1U << 4)
/* Device Control API: ARM VGIC */
#define KVM_DEV_ARM_VGIC_GRP_ADDR 0
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index d3842791e1c4..c00c17c9adb6 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -348,6 +348,20 @@ static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
return vcpu_read_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
}
+static inline bool kvm_arm_get_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.workaround_flags & VCPU_WORKAROUND_2_FLAG;
+}
+
+static inline void kvm_arm_set_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu,
+ bool flag)
+{
+ if (flag)
+ vcpu->arch.workaround_flags |= VCPU_WORKAROUND_2_FLAG;
+ else
+ vcpu->arch.workaround_flags &= ~VCPU_WORKAROUND_2_FLAG;
+}
+
static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
{
if (vcpu_mode_is_32bit(vcpu)) {
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 97c3478ee6e7..e75a81a7716f 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -225,6 +225,16 @@ struct kvm_vcpu_events {
#define KVM_REG_ARM_FW_REG(r) (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
KVM_REG_ARM_FW | ((r) & 0xffff))
#define KVM_REG_ARM_PSCI_VERSION KVM_REG_ARM_FW_REG(0)
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1 KVM_REG_ARM_FW_REG(1)
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL 0
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL 1
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_UNAFFECTED 2
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2 KVM_REG_ARM_FW_REG(2)
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL 0
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN 1
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL 2
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNAFFECTED 3
+#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED (1U << 4)
/* Device Control API: ARM VGIC */
#define KVM_DEV_ARM_VGIC_GRP_ADDR 0
diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 1da53e0e38f7..c82d90aad3ea 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -449,42 +449,103 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
{
- return 1; /* PSCI version */
+ return 3; /* PSCI version and two workaround registers */
}
int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
{
- if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices))
+ if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
+ return -EFAULT;
+
+ if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
+ return -EFAULT;
+
+ if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
return -EFAULT;
return 0;
}
+#define KVM_REG_FEATURE_LEVEL_WIDTH 4
+#define KVM_REG_FEATURE_LEVEL_MASK (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
+
+/*
+ * Convert the workaround level into an easy-to-compare number, where higher
+ * values mean better protection.
+ */
+static int get_kernel_wa_level(u64 regid)
+{
+ switch (regid) {
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
+ switch (kvm_arm_harden_branch_predictor()) {
+ case KVM_BP_HARDEN_UNKNOWN:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
+ case KVM_BP_HARDEN_NEEDED:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
+ case KVM_BP_HARDEN_MITIGATED:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_UNAFFECTED;
+ }
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
+ switch (kvm_arm_have_ssbd()) {
+ case KVM_SSBD_FORCE_DISABLE:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
+ case KVM_SSBD_KERNEL:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL;
+ case KVM_SSBD_FORCE_ENABLE:
+ case KVM_SSBD_MITIGATED:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNAFFECTED;
+ case KVM_SSBD_UNKNOWN:
+ default:
+ return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN;
+ }
+ }
+
+ return -EINVAL;
+}
+
int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
{
- if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
- void __user *uaddr = (void __user *)(long)reg->addr;
- u64 val;
+ void __user *uaddr = (void __user *)(long)reg->addr;
+ u64 val;
+ switch (reg->id) {
+ case KVM_REG_ARM_PSCI_VERSION:
val = kvm_psci_version(vcpu, vcpu->kvm);
- if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
- return -EFAULT;
+ break;
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
+ val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
+ break;
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
+ val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
- return 0;
+ if (val == KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL &&
+ kvm_arm_get_vcpu_workaround_2_flag(vcpu))
+ val |= KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED;
+ break;
+ default:
+ return -ENOENT;
}
- return -EINVAL;
+ if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ return 0;
}
int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
{
- if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
- void __user *uaddr = (void __user *)(long)reg->addr;
- bool wants_02;
- u64 val;
+ void __user *uaddr = (void __user *)(long)reg->addr;
+ u64 val;
+ int wa_level;
+
+ if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
- if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
- return -EFAULT;
+ switch (reg->id) {
+ case KVM_REG_ARM_PSCI_VERSION:
+ {
+ bool wants_02;
wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
@@ -501,6 +562,54 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
vcpu->kvm->arch.psci_version = val;
return 0;
}
+ break;
+ }
+
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
+ if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
+ return -EINVAL;
+
+ if (get_kernel_wa_level(reg->id) < val)
+ return -EINVAL;
+
+ return 0;
+
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
+ if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
+ return -EINVAL;
+
+ wa_level = val & KVM_REG_FEATURE_LEVEL_MASK;
+
+ if (get_kernel_wa_level(reg->id) < wa_level)
+ return -EINVAL;
+
+ /* The enabled bit must not be set unless the level is AVAIL. */
+ if (wa_level != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL &&
+ wa_level != val)
+ return -EINVAL;
+
+ /* Are we finished or do we need to check the enable bit ? */
+ if (kvm_arm_have_ssbd() != KVM_SSBD_KERNEL)
+ return 0;
+
+ /*
+ * If this kernel supports the workaround to be switched on
+ * or off, make sure it matches the requested setting.
+ */
+ switch (wa_level) {
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
+ kvm_arm_set_vcpu_workaround_2_flag(vcpu,
+ val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED);
+ break;
+ case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNAFFECTED:
+ kvm_arm_set_vcpu_workaround_2_flag(vcpu, true);
+ break;
+ }
+
+ return 0;
+ default:
+ return -ENOENT;
}
return -EINVAL;
--
2.17.1
