With per guest ID registers, ID_AA64PFR0_EL1.[CSV2|CSV3] settings from userspace can be stored in its corresponding ID register. The setting of CSV bits for protected VMs are removed according to the discussion from Fuad below: https://lore.kernel.org/all/CA+EHjTwXA9TprX4jeG+-D+c8v9XG+oFdU1o6TSkvVye145_OvA@xxxxxxxxxxxxxx Besides the removal of CSV bits setting for protected VMs, No other functional change intended. Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx> --- arch/arm64/include/asm/kvm_host.h | 2 -- arch/arm64/kvm/arm.c | 17 ---------- arch/arm64/kvm/id_regs.c | 56 ++++++++++++++++++++++++------- 3 files changed, 44 insertions(+), 31 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a7d4d9e093e3..4699f6b829b2 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -248,8 +248,6 @@ struct kvm_arch { cpumask_var_t supported_cpus; - u8 pfr0_csv2; - u8 pfr0_csv3; struct { u8 imp:4; u8 unimp:4; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index e34744c36406..0f71b10a2f05 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -104,22 +104,6 @@ static int kvm_arm_default_max_vcpus(void) return vgic_present ? kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS; } -static void set_default_spectre(struct kvm *kvm) -{ - /* - * The default is to expose CSV2 == 1 if the HW isn't affected. - * Although this is a per-CPU feature, we make it global because - * asymmetric systems are just a nuisance. - * - * Userspace can override this as long as it doesn't promise - * the impossible. - */ - if (arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED) - kvm->arch.pfr0_csv2 = 1; - if (arm64_get_meltdown_state() == SPECTRE_UNAFFECTED) - kvm->arch.pfr0_csv3 = 1; -} - /** * kvm_arch_init_vm - initializes a VM data structure * @kvm: pointer to the KVM struct @@ -151,7 +135,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) /* The maximum number of VCPUs is limited by the host's GIC model */ kvm->max_vcpus = kvm_arm_default_max_vcpus(); - set_default_spectre(kvm); kvm_arm_init_hypercalls(kvm); kvm_arm_init_id_regs(kvm); diff --git a/arch/arm64/kvm/id_regs.c b/arch/arm64/kvm/id_regs.c index e769223bcee2..5e0fd4c8b375 100644 --- a/arch/arm64/kvm/id_regs.c +++ b/arch/arm64/kvm/id_regs.c @@ -61,12 +61,6 @@ u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id) if (!vcpu_has_sve(vcpu)) val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_SVE); val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_AMU); - val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2); - val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2), - (u64)vcpu->kvm->arch.pfr0_csv2); - val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3); - val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3), - (u64)vcpu->kvm->arch.pfr0_csv3); if (kvm_vgic_global_state.type == VGIC_V3) { val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_GIC); val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_GIC), 1); @@ -153,7 +147,12 @@ static bool access_id_reg(struct kvm_vcpu *vcpu, static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, u64 *val) { + struct kvm_arch *arch = &vcpu->kvm->arch; + + mutex_lock(&arch->config_lock); *val = read_id_reg(vcpu, rd); + mutex_unlock(&arch->config_lock); + return 0; } @@ -200,7 +199,10 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, u64 val) { + struct kvm_arch *arch = &vcpu->kvm->arch; + u64 sval = val; u8 csv2, csv3; + int ret = 0; /* * Allow AA64PFR0_EL1.CSV2 to be set from userspace as long as @@ -216,17 +218,26 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, if (csv3 > 1 || (csv3 && arm64_get_meltdown_state() != SPECTRE_UNAFFECTED)) return -EINVAL; + mutex_lock(&arch->config_lock); /* We can only differ with CSV[23], and anything else is an error */ val ^= read_id_reg(vcpu, rd); val &= ~(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2) | ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3)); - if (val) - return -EINVAL; - - vcpu->kvm->arch.pfr0_csv2 = csv2; - vcpu->kvm->arch.pfr0_csv3 = csv3; + if (val) { + ret = -EINVAL; + goto out; + } - return 0; + /* Only allow userspace to change the idregs before VM running */ + if (test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &vcpu->kvm->arch.flags)) { + if (sval != read_id_reg(vcpu, rd)) + ret = -EBUSY; + } else { + IDREG(vcpu->kvm, reg_to_encoding(rd)) = sval; + } +out: + mutex_unlock(&arch->config_lock); + return ret; } static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu, @@ -485,4 +496,25 @@ void kvm_arm_init_id_regs(struct kvm *kvm) val = read_sanitised_ftr_reg(id); IDREG(kvm, id) = val; } + + /* + * The default is to expose CSV2 == 1 if the HW isn't affected. + * Although this is a per-CPU feature, we make it global because + * asymmetric systems are just a nuisance. + * + * Userspace can override this as long as it doesn't promise + * the impossible. + */ + val = IDREG(kvm, SYS_ID_AA64PFR0_EL1); + + if (arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED) { + val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2); + val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2), 1); + } + if (arm64_get_meltdown_state() == SPECTRE_UNAFFECTED) { + val &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3); + val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3), 1); + } + + IDREG(kvm, SYS_ID_AA64PFR0_EL1) = val; } -- 2.40.1.495.gc816e09b53d-goog
