diff options
| author | Marc Zyngier <maz@kernel.org> | 2025-02-20 16:49:03 +0300 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2025-02-24 22:30:17 +0300 |
| commit | f83c41fb3dddbf47881249335a9718d2cdce0bd0 (patch) | |
| tree | 5b1a7d2a7f8eb268e079ccfad5e35e9df4d73b7c | |
| parent | 94f296dcd6d937371dd83df048b9a2d723d357c9 (diff) | |
| download | linux-f83c41fb3dddbf47881249335a9718d2cdce0bd0.tar.xz | |
KVM: arm64: Allow userspace to limit NV support to nVHE
NV is hard. No kidding.
In order to make things simpler, we have established that NV would
support two mutually exclusive configurations:
- VHE-only, and supporting recursive virtualisation
- nVHE-only, and not supporting recursive virtualisation
For that purpose, introduce a new vcpu feature flag that denotes
the second configuration. We use this flag to limit the idregs
further.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20250220134907.554085-11-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
| -rw-r--r-- | arch/arm64/include/uapi/asm/kvm.h | 1 | ||||
| -rw-r--r-- | arch/arm64/kvm/nested.c | 28 |
2 files changed, 27 insertions, 2 deletions
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index 568bf858f319..3bcab2a106c9 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -105,6 +105,7 @@ struct kvm_regs { #define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ #define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ #define KVM_ARM_VCPU_HAS_EL2 7 /* Support nested virtualization */ +#define KVM_ARM_VCPU_HAS_EL2_E2H0 8 /* Limit NV support to E2H RES0 */ struct kvm_vcpu_init { __u32 target; diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 409e5e67ae1e..933dc3acac5f 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -51,6 +51,10 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu) struct kvm_s2_mmu *tmp; int num_mmus, ret = 0; + if (test_bit(KVM_ARM_VCPU_HAS_EL2_E2H0, kvm->arch.vcpu_features) && + !cpus_have_final_cap(ARM64_HAS_HCR_NV1)) + return -EINVAL; + /* * Let's treat memory allocation failures as benign: If we fail to * allocate anything, return an error and keep the allocated array @@ -894,6 +898,9 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val) ID_AA64MMFR1_EL1_HPDS | ID_AA64MMFR1_EL1_VH | ID_AA64MMFR1_EL1_VMIDBits); + /* FEAT_E2H0 implies no VHE */ + if (test_bit(KVM_ARM_VCPU_HAS_EL2_E2H0, kvm->arch.vcpu_features)) + val &= ~ID_AA64MMFR1_EL1_VH; break; case SYS_ID_AA64MMFR2_EL1: @@ -909,8 +916,25 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val) break; case SYS_ID_AA64MMFR4_EL1: - val = SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, NV_frac, NV2_ONLY); - val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, E2H0, NI_NV1); + /* + * You get EITHER + * + * - FEAT_VHE without FEAT_E2H0 + * - FEAT_NV limited to FEAT_NV2 + * - HCR_EL2.NV1 being RES0 + * + * OR + * + * - FEAT_E2H0 without FEAT_VHE nor FEAT_NV + * + * Life is too short for anything else. + */ + if (test_bit(KVM_ARM_VCPU_HAS_EL2_E2H0, kvm->arch.vcpu_features)) { + val = 0; + } else { + val = SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, NV_frac, NV2_ONLY); + val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, E2H0, NI_NV1); + } break; case SYS_ID_AA64DFR0_EL1: |