Hi Andrew,
On 12/06/2019 20:04, 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 | 19 +++++++++----------
> 2 files changed, 9 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..88ce24ae0b45 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);
Shouldn't this depend on PMCR.LC as well? If PMCR.LC is clear we only
want the lower 32bits of the cycle counter.
Cheers,
--
Julien Thierry
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