From: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
In order to match host and guest events, a mapping between guest VCPU
and the host task, running this VCPU is needed. Extended existing
struct guest to hold such mapping and added logic in read_qemu_guests()
function to initialize it. Implemented a new internal API,
get_guest_vcpu_pid(), to retrieve VCPU-task mapping for given VM.
Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
---
tracecmd/include/trace-local.h | 2 +
tracecmd/trace-record.c | 84 ++++++++++++++++++++++++++++++++++
2 files changed, 86 insertions(+)
diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
index 29f27793..a5cf0640 100644
--- a/tracecmd/include/trace-local.h
+++ b/tracecmd/include/trace-local.h
@@ -247,6 +247,8 @@ void update_first_instance(struct buffer_instance *instance, int topt);
void show_instance_file(struct buffer_instance *instance, const char *name);
+int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu);
+
/* moved from trace-cmd.h */
void tracecmd_create_top_instance(char *name);
void tracecmd_remove_instances(void);
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 0a3851ad..3cbc832c 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -3035,11 +3035,32 @@ struct guest {
char *name;
int cid;
int pid;
+ int cpu_max;
+ int *cpu_pid;
};
static struct guest *guests;
static size_t guests_len;
+static int set_vcpu_pid_mapping(struct guest *guest, int cpu, int pid)
+{
+ int *cpu_pid;
+ int i;
+
+ if (cpu >= guest->cpu_max) {
+ cpu_pid = realloc(guest->cpu_pid, (cpu + 1) * sizeof(int));
+ if (!cpu_pid)
+ return -1;
+ /* Handle sparse CPU numbers */
+ for (i = guest->cpu_max; i < cpu; i++)
+ guest->cpu_pid[i] = -1;
+ guest->cpu_max = cpu + 1;
+ guest->cpu_pid = cpu_pid;
+ }
+ guest->cpu_pid[cpu] = pid;
+ return 0;
+}
+
static char *get_qemu_guest_name(char *arg)
{
char *tok, *end = arg;
@@ -3052,6 +3073,49 @@ static char *get_qemu_guest_name(char *arg)
return arg;
}
+static int read_qemu_guests_pids(char *guest_task, struct guest *guest)
+{
+ struct dirent *entry;
+ char path[PATH_MAX];
+ char *buf = NULL;
+ size_t n = 0;
+ long vcpu;
+ long pid;
+ DIR *dir;
+ FILE *f;
+
+ snprintf(path, sizeof(path), "/proc/%s/task", guest_task);
+ dir = opendir(path);
+ if (!dir)
+ return -1;
+
+ while ((entry = readdir(dir))) {
+ if (!(entry->d_type == DT_DIR && is_digits(entry->d_name)))
+ continue;
+
+ snprintf(path, sizeof(path), "/proc/%s/task/%s/comm",
+ guest_task, entry->d_name);
+ f = fopen(path, "r");
+ if (!f)
+ continue;
+
+ if (getline(&buf, &n, f) >= 0 &&
+ strncmp(buf, "CPU ", 4) == 0) {
+ vcpu = strtol(buf + 4, NULL, 10);
+ pid = strtol(entry->d_name, NULL, 10);
+ if (vcpu < INT_MAX && pid < INT_MAX &&
+ vcpu >= 0 && pid >= 0) {
+ if (set_vcpu_pid_mapping(guest, vcpu, pid))
+ return -1;
+ }
+ }
+
+ fclose(f);
+ }
+ free(buf);
+ return 0;
+}
+
static void read_qemu_guests(void)
{
static bool initialized;
@@ -3115,6 +3179,10 @@ static void read_qemu_guests(void)
if (!is_qemu)
goto next;
+ if (read_qemu_guests_pids(entry->d_name, &guest))
+ warning("Failed to retrieve VPCU - PID mapping for guest %s",
+ guest.name ? guest.name : "Unknown");
+
guests = realloc(guests, (guests_len + 1) * sizeof(*guests));
if (!guests)
die("Can not allocate guest buffer");
@@ -3160,6 +3228,22 @@ static char *parse_guest_name(char *guest, int *cid, int *port)
return guest;
}
+int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu)
+{
+ int i;
+
+ if (!guests)
+ return -1;
+
+ for (i = 0; i < guests_len; i++) {
+ if (guests[i].cpu_pid < 0 || guest_vcpu >= guests[i].cpu_max)
+ continue;
+ if (guest_cid == guests[i].cid)
+ return guests[i].cpu_pid[guest_vcpu];
+ }
+ return -1;
+}
+
static void set_prio(int prio)
{
struct sched_param sp;
--
2.24.1
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