On 22/05/2019 16:30, Andrew Murray wrote:
> We currently use pmc->bitmask to determine the width of the pmc - however
> it's superfluous as the pmc index already describes if the pmc is a cycle
> counter or event counter. The architecture clearly describes the widths of
> these counters.
>
> Let's remove the bitmask to simplify the code.
>
> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> ---
> include/kvm/arm_pmu.h | 1 -
> virt/kvm/arm/pmu.c | 15 +++++----------
> 2 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index b73f31baca52..2f0e28dc5a9e 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -28,7 +28,6 @@
> struct kvm_pmc {
> u8 idx; /* index into the pmu->pmc array */
> struct perf_event *perf_event;
> - u64 bitmask;
> };
>
> struct kvm_pmu {
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index ae1e886d4a1a..c4e2bc213617 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -47,7 +47,10 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
> counter += perf_event_read_value(pmc->perf_event, &enabled,
> &running);
>
> - return counter & pmc->bitmask;
> + if (select_idx != ARMV8_PMU_CYCLE_IDX)
> + counter = lower_32_bits(counter);
> +
> + return counter;
> }
>
> /**
> @@ -113,7 +116,6 @@ void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
> for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
> kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]);
> pmu->pmc[i].idx = i;
> - pmu->pmc[i].bitmask = 0xffffffffUL;
> }
> }
>
> @@ -348,8 +350,6 @@ void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
> */
> void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
> {
> - struct kvm_pmu *pmu = &vcpu->arch.pmu;
> - struct kvm_pmc *pmc;
> u64 mask;
> int i;
>
> @@ -368,11 +368,6 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
> for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++)
> kvm_pmu_set_counter_value(vcpu, i, 0);
> }
> -
> - if (val & ARMV8_PMU_PMCR_LC) {
> - pmc = &pmu->pmc[ARMV8_PMU_CYCLE_IDX];
> - pmc->bitmask = 0xffffffffffffffffUL;
> - }
> }
>
> static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx)
> @@ -420,7 +415,7 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
>
> counter = kvm_pmu_get_counter_value(vcpu, select_idx);
> /* The initial sample period (overflow count) of an event. */
> - attr.sample_period = (-counter) & pmc->bitmask;
> + attr.sample_period = (-counter) & GENMASK(31, 0);
Isn't this the one case where the bitmask actually matters? If we're
dealing with the cycle counter, it shouldn't be truncated, right?
>
> event = perf_event_create_kernel_counter(&attr, -1, current,
> kvm_pmu_perf_overflow, pmc);
>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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