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 <[email protected]> Reviewed-by: Eric Auger <[email protected]> Reviewed-by: Steven Price <[email protected]> --- 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..a4217c1a5d01 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_NOT_REQUIRED 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_NOT_REQUIRED 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..2179783362a8 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_NOT_REQUIRED 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_NOT_REQUIRED 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 900b67c2720f..9d7c0130a156 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_WA_NEEDED: + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL; + case KVM_BP_HARDEN_NOT_REQUIRED: + return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED; + } + 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_NOT_REQUIRED; + 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_NOT_REQUIRED: + kvm_arm_set_vcpu_workaround_2_flag(vcpu, true); + break; + } + + return 0; + default: + return -ENOENT; } return -EINVAL; -- 2.17.1 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
