[RFC PATCH v4 22/26] KVM: arm64: Trap disabled features of ID_AA64DFR0_EL1

[Fuad Tabba]

.Hi Reiji,

On Thu, Jan 6, 2022 at 4:29 AM Reiji Watanabe <reijiw at google.com> wrote:
>
> Add feature_config_ctrl for PMUv3, PMS and TraceFilt, which are
> indicated in ID_AA64DFR0_EL1, to program configuration registers
> to trap guest's using those features when they are not exposed to
> the guest.
>
> Signed-off-by: Reiji Watanabe <reijiw at google.com>
> ---
>  arch/arm64/kvm/sys_regs.c | 47 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 72e745c5a9c2..229671ec3abd 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -349,6 +349,22 @@ static void feature_mte_trap_activate(struct kvm_vcpu *vcpu)
>         feature_trap_activate(vcpu, VCPU_HCR_EL2, HCR_TID5, HCR_DCT | HCR_ATA);
>  }
>
> +static void feature_pmuv3_trap_activate(struct kvm_vcpu *vcpu)
> +{
> +       feature_trap_activate(vcpu, VCPU_MDCR_EL2, MDCR_EL2_TPM, 0);

I think that for full coverage it might be good to include setting
MDCR_EL2_TPMCR, and clearing MDCR_EL2_HPME | MDCR_EL2_MTPME |
MDCR_EL2_HPMN_MASK, even if redundant at this point.

> +}
> +
> +static void feature_pms_trap_activate(struct kvm_vcpu *vcpu)
> +{
> +       feature_trap_activate(vcpu, VCPU_MDCR_EL2, MDCR_EL2_TPMS,
> +                             MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT);
> +}
> +
> +static void feature_tracefilt_trap_activate(struct kvm_vcpu *vcpu)
> +{
> +       feature_trap_activate(vcpu, VCPU_MDCR_EL2, MDCR_EL2_TTRF, 0);
> +}
> +
>  /* For ID_AA64PFR0_EL1 */
>  static struct feature_config_ctrl ftr_ctrl_ras = {
>         .ftr_reg = SYS_ID_AA64PFR0_EL1,
> @@ -375,6 +391,31 @@ static struct feature_config_ctrl ftr_ctrl_mte = {
>         .trap_activate = feature_mte_trap_activate,
>  };
>
> +/* For ID_AA64DFR0_EL1 */
> +static struct feature_config_ctrl ftr_ctrl_pmuv3 = {
> +       .ftr_reg = SYS_ID_AA64DFR0_EL1,
> +       .ftr_shift = ID_AA64DFR0_PMUVER_SHIFT,
> +       .ftr_min = ID_AA64DFR0_PMUVER_8_0,
> +       .ftr_signed = FTR_UNSIGNED,
> +       .trap_activate = feature_pmuv3_trap_activate,
> +};
> +
> +static struct feature_config_ctrl ftr_ctrl_pms = {
> +       .ftr_reg = SYS_ID_AA64DFR0_EL1,
> +       .ftr_shift = ID_AA64DFR0_PMSVER_SHIFT,
> +       .ftr_min = ID_AA64DFR0_PMSVER_8_2,
> +       .ftr_signed = FTR_UNSIGNED,
> +       .trap_activate = feature_pms_trap_activate,
> +};
> +
> +static struct feature_config_ctrl ftr_ctrl_tracefilt = {
> +       .ftr_reg = SYS_ID_AA64DFR0_EL1,
> +       .ftr_shift = ID_AA64DFR0_TRACE_FILT_SHIFT,
> +       .ftr_min = 1,
> +       .ftr_signed = FTR_UNSIGNED,
> +       .trap_activate = feature_tracefilt_trap_activate,
> +};

I think you might be missing trace, ID_AA64DFR0_TRACEVER -> CPTR_EL2_TTA.

Cheers,
/fuad


> +
>  struct id_reg_info {
>         u32     sys_reg;        /* Register ID */
>         u64     sys_val;        /* Sanitized system value */
> @@ -898,6 +939,12 @@ static struct id_reg_info id_aa64dfr0_el1_info = {
>         .init = init_id_aa64dfr0_el1_info,
>         .validate = validate_id_aa64dfr0_el1,
>         .vcpu_mask = vcpu_mask_id_aa64dfr0_el1,
> +       .trap_features = &(const struct feature_config_ctrl *[]) {
> +               &ftr_ctrl_pmuv3,
> +               &ftr_ctrl_pms,
> +               &ftr_ctrl_tracefilt,
> +               NULL,
> +       },
>  };
>
>  static struct id_reg_info id_dfr0_el1_info = {
> --
> 2.34.1.448.ga2b2bfdf31-goog
>
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