perf tools: Add guest_cpu to hypervisor threads

It is possible to know which guest machine was running at a point in time
based on the PID of the currently running host thread. That is, perf
identifies guest machines by the PID of the hypervisor.

To determine the guest CPU, put it on the hypervisor (QEMU) thread for
that VCPU.

This is done when processing the id_index which provides the necessary
information.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-13-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 1af981d5ad3c..91a091c35945 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -2769,6 +2769,20 @@ static int perf_session__register_guest(struct perf_session *session, pid_t mach
 	return 0;
 }
 
+static int perf_session__set_guest_cpu(struct perf_session *session, pid_t pid,
+				       pid_t tid, int guest_cpu)
+{
+	struct machine *machine = &session->machines.host;
+	struct thread *thread = machine__findnew_thread(machine, pid, tid);
+
+	if (!thread)
+		return -ENOMEM;
+	thread->guest_cpu = guest_cpu;
+	thread__put(thread);
+
+	return 0;
+}
+
 int perf_event__process_id_index(struct perf_session *session,
 				 union perf_event *event)
 {
@@ -2845,6 +2859,10 @@ int perf_event__process_id_index(struct perf_session *session,
 			last_pid = sid->machine_pid;
 			perf_guest = true;
 		}
+
+		ret = perf_session__set_guest_cpu(session, sid->machine_pid, e->tid, e2->vcpu);
+		if (ret)
+			return ret;
 	}
 	return 0;
 }