Re: [PATCH 4/9] KVM: arm64: PMU: Add counter_index_to_*reg() helpers

[Reiji Watanabe <reijiw@google.com>]

Hi Marc,

On Fri, Aug 5, 2022 at 6:58 AM Marc Zyngier <maz@kernel.org> wrote:
>
> In order to reduce the boilerplate code, add two helpers returning
> the counter register index (resp. the event register) in the vcpu
> register file from the counter index.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/pmu-emul.c | 27 +++++++++++++++------------
>  1 file changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> index 0ab6f59f433c..9be485d23416 100644
> --- a/arch/arm64/kvm/pmu-emul.c
> +++ b/arch/arm64/kvm/pmu-emul.c
> @@ -75,6 +75,16 @@ static struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
>         return container_of(vcpu_arch, struct kvm_vcpu, arch);
>  }
>
> +static u32 counter_index_to_reg(u64 idx)
> +{
> +       return (idx == ARMV8_PMU_CYCLE_IDX) ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + idx;
> +}
> +
> +static u32 counter_index_to_evtreg(u64 idx)
> +{
> +       return (idx == ARMV8_PMU_CYCLE_IDX) ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + idx;
> +}
> +
>  /**
>   * kvm_pmu_get_counter_value - get PMU counter value
>   * @vcpu: The vcpu pointer
> @@ -89,8 +99,7 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
>         if (!kvm_vcpu_has_pmu(vcpu))
>                 return 0;
>
> -       reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> -               ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
> +       reg = counter_index_to_reg(select_idx);
>         counter = __vcpu_sys_reg(vcpu, reg);
>
>         /*
> @@ -120,8 +129,7 @@ void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
>         if (!kvm_vcpu_has_pmu(vcpu))
>                 return;
>
> -       reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> -             ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx;
> +       reg = counter_index_to_reg(select_idx);
>         __vcpu_sys_reg(vcpu, reg) += (s64)val - kvm_pmu_get_counter_value(vcpu, select_idx);
>
>         /* Recreate the perf event to reflect the updated sample_period */
> @@ -156,10 +164,7 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
>
>         counter = kvm_pmu_get_counter_value(vcpu, pmc->idx);
>
> -       if (pmc->idx == ARMV8_PMU_CYCLE_IDX)
> -               reg = PMCCNTR_EL0;
> -       else
> -               reg = PMEVCNTR0_EL0 + pmc->idx;
> +       reg = counter_index_to_reg(pmc->idx);
>
>         if (!kvm_pmu_idx_is_64bit(vcpu, pmc->idx))
>                 counter = lower_32_bits(counter);
> @@ -540,8 +545,7 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
>         struct perf_event_attr attr;
>         u64 eventsel, counter, reg, data;
>
> -       reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> -             ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + pmc->idx;
> +       reg = counter_index_to_evtreg(select_idx);
>         data = __vcpu_sys_reg(vcpu, reg);
>
>         kvm_pmu_stop_counter(vcpu, pmc);
> @@ -627,8 +631,7 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
>         mask &= ~ARMV8_PMU_EVTYPE_EVENT;
>         mask |= kvm_pmu_event_mask(vcpu->kvm);
>
> -       reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
> -             ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;
> +       reg = counter_index_to_evtreg(select_idx);
>
>         __vcpu_sys_reg(vcpu, reg) = data & mask;
>
> --

counter_index_to_evtreg() could also be used in access_pmu_evtyper()
in sys_regs.c (counter_index_to_evtreg() is currently defined as
static in pmu-emul.c though).

---
static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
                               const struct sys_reg_desc *r)
{
        <...>
        } else if (r->CRn == 14 && (r->CRm & 12) == 12) {
                idx = ((r->CRm & 3) << 3) | (r->Op2 & 7);
                if (idx == ARMV8_PMU_CYCLE_IDX)
                        reg = PMCCFILTR_EL0;
                else
                        /* PMEVTYPERn_EL0 */
                        reg = PMEVTYPER0_EL0 + idx;
        <...>
---

Thank you,
Reiji