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authorColton Lewis <coltonlewis@google.com>2024-11-13 19:01:55 +0000
committerIngo Molnar <mingo@kernel.org>2024-11-14 10:40:01 +0100
commit2c47e7a74f445426d156278e339b7abb259e50de (patch)
tree79794357b4d4ad9e9ced2172d508b30259946734 /kernel
parentbaff01f3d75ff3948a0465853dcaa71c394c5c46 (diff)
perf/core: Correct perf sampling with guest VMs
Previously any PMU overflow interrupt that fired while a VCPU was loaded was recorded as a guest event whether it truly was or not. This resulted in nonsense perf recordings that did not honor perf_event_attr.exclude_guest and recorded guest IPs where it should have recorded host IPs. Rework the sampling logic to only record guest samples for events with exclude_guest = 0. This way any host-only events with exclude_guest set will never see unexpected guest samples. The behaviour of events with exclude_guest = 0 is unchanged. Note that events configured to sample both host and guest may still misattribute a PMI that arrived in the host as a guest event depending on KVM arch and vendor behavior. Signed-off-by: Colton Lewis <coltonlewis@google.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Kan Liang <kan.liang@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20241113190156.2145593-6-coltonlewis@google.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6050ce033ead..1869164a4e99 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7026,13 +7026,26 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
#endif
-unsigned long perf_misc_flags(struct pt_regs *regs)
+static bool should_sample_guest(struct perf_event *event)
{
+ return !event->attr.exclude_guest && perf_guest_state();
+}
+
+unsigned long perf_misc_flags(struct perf_event *event,
+ struct pt_regs *regs)
+{
+ if (should_sample_guest(event))
+ return perf_arch_guest_misc_flags(regs);
+
return perf_arch_misc_flags(regs);
}
-unsigned long perf_instruction_pointer(struct pt_regs *regs)
+unsigned long perf_instruction_pointer(struct perf_event *event,
+ struct pt_regs *regs)
{
+ if (should_sample_guest(event))
+ return perf_guest_get_ip();
+
return perf_arch_instruction_pointer(regs);
}
@@ -7853,7 +7866,7 @@ void perf_prepare_sample(struct perf_sample_data *data,
__perf_event_header__init_id(data, event, filtered_sample_type);
if (filtered_sample_type & PERF_SAMPLE_IP) {
- data->ip = perf_instruction_pointer(regs);
+ data->ip = perf_instruction_pointer(event, regs);
data->sample_flags |= PERF_SAMPLE_IP;
}
@@ -8017,7 +8030,7 @@ void perf_prepare_header(struct perf_event_header *header,
{
header->type = PERF_RECORD_SAMPLE;
header->size = perf_sample_data_size(data, event);
- header->misc = perf_misc_flags(regs);
+ header->misc = perf_misc_flags(event, regs);
/*
* If you're adding more sample types here, you likely need to do