On 18/11/2021 11:00 pm, Paolo Bonzini wrote:
On 11/16/21 13:20, Like Xu wrote:
+static inline unsigned int intel_find_fixed_event(int idx)
+{
+ u32 event;
+ size_t size = ARRAY_SIZE(fixed_pmc_events);
+
+ if (idx >= size)
+ return PERF_COUNT_HW_MAX;
+
+ event = fixed_pmc_events[array_index_nospec(idx, size)];
+ return intel_arch_events[event].event_type;
+}
+
+
static unsigned int intel_find_perf_hw_id(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -75,6 +88,9 @@ static unsigned int intel_find_perf_hw_id(struct kvm_pmc *pmc)
u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
int i;
+ if (pmc_is_fixed(pmc))
+ return intel_find_fixed_event(pmc->idx - INTEL_PMC_IDX_FIXED);
Is intel_find_fixed_event needed at all? As you point out in the commit
message, eventsel/unit_mask are valid so you can do
@@ -88,13 +75,11 @@ static unsigned int intel_pmc_perf_hw_id(struct kvm_pmc *pmc)
u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
int i;
- if (pmc_is_fixed(pmc))
- return intel_find_fixed_event(pmc->idx - INTEL_PMC_IDX_FIXED);
-
for (i = 0; i < ARRAY_SIZE(intel_arch_events); i++)
if (intel_arch_events[i].eventsel == event_select
&& intel_arch_events[i].unit_mask == unit_mask
- && (pmu->available_event_types & (1 << i)))
+ && (pmc_is_fixed(pmc) ||
+ pmu->available_event_types & (1 << i)))
It's a good move while the tricky thing I've found recently is:
the events masked in pmu->available_event_types are just *Intel CPUID* events
(they're not a subset or superset of the *kernel generic* hw events),
some of which can be programmed and enabled with generic or fixed counter.
According Intel SDM, when an Intel CPUID event (e.g. "instructions retirement")
is not masked in pmu->available_event_types (configured via Intel CPUID.0A.EBX),
the guest should not use generic or fixed counter to count/sample this event.
This issue is detailed in another patch set [1] and comments need to be collected.
It's proposed to get [V2] merged and continue to review the fixes from [1]
seamlessly,
and then further unify all fixed/gp stuff including intel_find_fixed_event() as
a follow up.
[1] https://lore.kernel.org/kvm/20211112095139.21775-1-likexu@xxxxxxxxxxx/
[V2] https://lore.kernel.org/kvm/20211119064856.77948-1-likexu@xxxxxxxxxxx/
break;
if (i == ARRAY_SIZE(intel_arch_events))
What do you think? It's less efficient but makes fixed/gp more similar.
Can you please resubmit the series based on the review feedback?
Thanks,
