On 13/06/2019 10:39, Andrew Murray wrote:
On Thu, Jun 13, 2019 at 08:30:51AM +0100, Julien Thierry wrote:
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.
Yes that's correct. The hunk should look like this:
- return counter & pmc->bitmask;
+ if (!(select_idx == ARMV8_PMU_CYCLE_IDX &&
+ __vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_LC))
+ counter = lower_32_bits(counter);
+
+ return counter;
May be you could add a macro :
#define vcpu_pmu_counter_is_64bit(vcpu, idx) ?
Cheers
Suzuki
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