[RFC PATCH v4 14/26] KVM: arm64: Add consistency checking for frac fields of ID registers
Fuad Tabba
tabba at google.com
Mon Jan 24 09:00:38 PST 2022
Hi Reiji,
On Thu, Jan 6, 2022 at 4:29 AM Reiji Watanabe <reijiw at google.com> wrote:
>
> Feature fractional field of an ID register cannot be simply validated
> at KVM_SET_ONE_REG because its validity depends on its (main) feature
> field value, which could be in a different ID register (and might be
> set later).
> Validate fractional fields at the first KVM_RUN instead.
>
> Signed-off-by: Reiji Watanabe <reijiw at google.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 1 +
> arch/arm64/kvm/arm.c | 3 +
> arch/arm64/kvm/sys_regs.c | 116 +++++++++++++++++++++++++++++-
> 3 files changed, 117 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 4509f9e7472d..7b3f86bd6a6b 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -750,6 +750,7 @@ long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
>
> void set_default_id_regs(struct kvm *kvm);
> int kvm_set_id_reg_feature(struct kvm *kvm, u32 id, u8 field_shift, u8 fval);
> +int kvm_id_regs_consistency_check(const struct kvm_vcpu *vcpu);
>
> /* Guest/host FPSIMD coordination helpers */
> int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 5f497a0af254..16fc2ce32069 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -596,6 +596,9 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
> if (!kvm_arm_vcpu_is_finalized(vcpu))
> return -EPERM;
>
> + if (!kvm_vm_is_protected(kvm) && kvm_id_regs_consistency_check(vcpu))
> + return -EPERM;
> +
> vcpu->arch.has_run_once = true;
>
> kvm_arm_vcpu_init_debug(vcpu);
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index ddbeefc3881c..6adb7b04620c 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -756,9 +756,6 @@ static struct id_reg_info id_aa64pfr0_el1_info = {
>
> static struct id_reg_info id_aa64pfr1_el1_info = {
> .sys_reg = SYS_ID_AA64PFR1_EL1,
> - .ignore_mask = ARM64_FEATURE_MASK(ID_AA64PFR1_RASFRAC) |
> - ARM64_FEATURE_MASK(ID_AA64PFR1_MPAMFRAC) |
> - ARM64_FEATURE_MASK(ID_AA64PFR1_CSV2FRAC),
> .init = init_id_aa64pfr1_el1_info,
> .validate = validate_id_aa64pfr1_el1,
> .vcpu_mask = vcpu_mask_id_aa64pfr1_el1,
> @@ -3434,10 +3431,109 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
> return write_demux_regids(uindices);
> }
>
> +/* ID register's fractional field information with its feature field. */
> +struct feature_frac {
> + u32 id;
> + u32 shift;
> + u32 frac_id;
> + u32 frac_shift;
> + u8 frac_ftr_check;
> +};
frac_ftr_check doesn't seem to be used. Also, it would be easier to
read if the ordering of the fields match the ordering you initialize
them below.
> +
> +static struct feature_frac feature_frac_table[] = {
> + {
> + .frac_id = SYS_ID_AA64PFR1_EL1,
> + .frac_shift = ID_AA64PFR1_RASFRAC_SHIFT,
> + .id = SYS_ID_AA64PFR0_EL1,
> + .shift = ID_AA64PFR0_RAS_SHIFT,
> + },
> + {
> + .frac_id = SYS_ID_AA64PFR1_EL1,
> + .frac_shift = ID_AA64PFR1_MPAMFRAC_SHIFT,
> + .id = SYS_ID_AA64PFR0_EL1,
> + .shift = ID_AA64PFR0_MPAM_SHIFT,
> + },
> + {
> + .frac_id = SYS_ID_AA64PFR1_EL1,
> + .frac_shift = ID_AA64PFR1_CSV2FRAC_SHIFT,
> + .id = SYS_ID_AA64PFR0_EL1,
> + .shift = ID_AA64PFR0_CSV2_SHIFT,
> + },
> +};
> +
> +/*
> + * Return non-zero if the feature/fractional fields pair are not
> + * supported. Return zero otherwise.
> + * This function validates only the fractional feature field,
> + * and relies on the fact the feature field is validated before
> + * through arm64_check_features.
> + */
> +static int vcpu_id_reg_feature_frac_check(const struct kvm_vcpu *vcpu,
> + const struct feature_frac *ftr_frac)
> +{
> + const struct id_reg_info *id_reg;
> + u32 id;
> + u64 val, lim, mask;
> +
> + /* Check if the feature field value is same as the limit */
> + id = ftr_frac->id;
> + id_reg = GET_ID_REG_INFO(id);
> +
> + mask = (u64)ARM64_FEATURE_FIELD_MASK << ftr_frac->shift;
> + val = __read_id_reg(vcpu, id) & mask;
> + lim = id_reg ? id_reg->vcpu_limit_val : read_sanitised_ftr_reg(id);
> + lim &= mask;
> +
> + if (val != lim)
> + /*
> + * The feature level is lower than the limit.
> + * Any fractional version should be fine.
> + */
> + return 0;
> +
> + /* Check the fractional feature field */
> + id = ftr_frac->frac_id;
> + id_reg = GET_ID_REG_INFO(id);
> +
> + mask = (u64)ARM64_FEATURE_FIELD_MASK << ftr_frac->frac_shift;
> + val = __read_id_reg(vcpu, id) & mask;
> + lim = id_reg ? id_reg->vcpu_limit_val : read_sanitised_ftr_reg(id);
> + lim &= mask;
> +
> + if (val == lim)
> + /*
> + * Both the feature and fractional fields are the same
> + * as limit.
> + */
> + return 0;
> +
> + return arm64_check_features(id, val, lim);
> +}
> +
> +int kvm_id_regs_consistency_check(const struct kvm_vcpu *vcpu)
Nit: considering that this is only checking the fractional fields,
should the function name reflect that?
> +{
> + int i, err;
> + const struct feature_frac *frac;
> +
> + /*
> + * Check ID registers' fractional fields, which aren't checked
> + * at KVM_SET_ONE_REG.
> + */
> + for (i = 0; i < ARRAY_SIZE(feature_frac_table); i++) {
> + frac = &feature_frac_table[i];
> + err = vcpu_id_reg_feature_frac_check(vcpu, frac);
> + if (err)
> + return err;
> + }
> + return 0;
> +}
> +
> static void id_reg_info_init_all(void)
> {
> int i;
> struct id_reg_info *id_reg;
> + struct feature_frac *frac;
> + u64 ftr_mask = ARM64_FEATURE_FIELD_MASK;
>
> for (i = 0; i < ARRAY_SIZE(id_reg_info_table); i++) {
> id_reg = (struct id_reg_info *)id_reg_info_table[i];
> @@ -3446,6 +3542,20 @@ static void id_reg_info_init_all(void)
>
> id_reg_info_init(id_reg);
> }
> +
> + /*
> + * Update ignore_mask of ID registers based on fractional fields
> + * information. Any ID register that have fractional fields
> + * is expected to have its own id_reg_info.
> + */
> + for (i = 0; i < ARRAY_SIZE(feature_frac_table); i++) {
> + frac = &feature_frac_table[i];
> + id_reg = GET_ID_REG_INFO(frac->frac_id);
> + if (WARN_ON_ONCE(!id_reg))
> + continue;
> +
> + id_reg->ignore_mask |= ftr_mask << frac->frac_shift;
> + }
> }
Thanks,
/fuad
>
> void kvm_sys_reg_table_init(void)
> --
> 2.34.1.448.ga2b2bfdf31-goog
>
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