Hi Jing, On Wed, May 17, 2023 at 06:10:11AM +0000, Jing Zhang wrote: > 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/sys_regs.c | 55 +++++++++++++++++++++++++------ > 3 files changed, 45 insertions(+), 29 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 949a4a782844..07f0e091ae48 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -257,8 +257,6 @@ 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 774656a0718d..5114521ace60 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -102,22 +102,6 @@ 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 > @@ -161,7 +145,6 @@ 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/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index d2ee3a1c7f03..3c52b136ade3 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1218,10 +1218,6 @@ static 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); > @@ -1359,7 +1355,10 @@ 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 > @@ -1377,17 +1376,26 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, > (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)) { How about using kvm_vm_has_ran_once() instead ? > + if (sval != read_id_reg(vcpu, rd)) Rather than calling read_id_reg() twice in this function, perhaps you might want to save the original val we got earlier and re-use it here ? Thank you, Reiji > + 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, > @@ -1479,7 +1487,12 @@ static int set_id_dfr0_el1(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; > } > > @@ -3364,6 +3377,7 @@ void kvm_arm_init_id_regs(struct kvm *kvm) > { > const struct sys_reg_desc *idreg; > struct sys_reg_params params; > + u64 val; > u32 id; > > /* Find the first idreg (SYS_ID_PFR0_EL1) in sys_reg_descs. */ > @@ -3386,6 +3400,27 @@ void kvm_arm_init_id_regs(struct kvm *kvm) > idreg++; > id = reg_to_encoding(idreg); > } > + > + /* > + * 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; > } > > int __init kvm_sys_reg_table_init(void) > -- > 2.40.1.606.ga4b1b128d6-goog >
