On Thu, Jan 02, 2020 at 12:39:04PM +0000, Andrew Murray wrote:
> ARMv8.5-PMU introduces 64-bit event counters, however KVM doesn't yet
> support this. Let's trap the Debug Feature Registers in order to limit
> PMUVer/PerfMon in the Debug Feature Registers to PMUv3 for ARMv8.4.
>
> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> arch/arm64/include/asm/sysreg.h | 4 ++++
> arch/arm64/kvm/sys_regs.c | 36 +++++++++++++++++++++++++++++++--
> 2 files changed, 38 insertions(+), 2 deletions(-)
I'll need an ack from the kvm side for this.
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 6e919fafb43d..1b74f275a115 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -672,6 +672,10 @@
> #define ID_AA64DFR0_TRACEVER_SHIFT 4
> #define ID_AA64DFR0_DEBUGVER_SHIFT 0
>
> +#define ID_DFR0_PERFMON_SHIFT 24
> +
> +#define ID_DFR0_EL1_PMUVER_8_4 5
> +
> #define ID_ISAR5_RDM_SHIFT 24
> #define ID_ISAR5_CRC32_SHIFT 16
> #define ID_ISAR5_SHA2_SHIFT 12
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 9f2165937f7d..61b984d934d1 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -668,6 +668,37 @@ static bool pmu_access_event_counter_el0_disabled(struct kvm_vcpu *vcpu)
> return check_pmu_access_disabled(vcpu, ARMV8_PMU_USERENR_ER | ARMV8_PMU_USERENR_EN);
> }
>
> +static bool access_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *p,
> + const struct sys_reg_desc *rd)
> +{
> + if (p->is_write)
> + return write_to_read_only(vcpu, p, rd);
> +
> + /* Limit guests to PMUv3 for ARMv8.4 */
> + p->regval = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
> + p->regval = cpuid_feature_cap_signed_field_width(p->regval,
> + ID_AA64DFR0_PMUVER_SHIFT,
> + 4, ID_DFR0_EL1_PMUVER_8_4);
nit: I'd probably have a separate define for the field value of the 64-bit
register, since there's no guarantee other values will be encoded the same
way. (i.e. add ID_AA64DFR0_PMUVER_8_4 as well).
> +
> + return p->regval;
> +}
> +
> +static bool access_id_dfr0_el1(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> + const struct sys_reg_desc *rd)
> +{
> + if (p->is_write)
> + return write_to_read_only(vcpu, p, rd);
> +
> + /* Limit guests to PMUv3 for ARMv8.4 */
> + p->regval = read_sanitised_ftr_reg(SYS_ID_DFR0_EL1);
> + p->regval = cpuid_feature_cap_signed_field_width(p->regval,
You could just return the result here (same above).
Will
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