From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
If the kvm vcpuX files do not map directly to the guest's CPUs, then the
tmaps will not match and the host will not have a mapping to the guest.
That is, if the hypervisor has:
# ls -d /sys/kernel/debug/kvm/[0-9]*/vcpu*
/sys/kernel/debug/kvm/408-7/vcpu0 /sys/kernel/debug/kvm/408-7/vcpu24
/sys/kernel/debug/kvm/408-7/vcpu1 /sys/kernel/debug/kvm/408-7/vcpu26
/sys/kernel/debug/kvm/408-7/vcpu16 /sys/kernel/debug/kvm/408-7/vcpu28
/sys/kernel/debug/kvm/408-7/vcpu18 /sys/kernel/debug/kvm/408-7/vcpu30
/sys/kernel/debug/kvm/408-7/vcpu20 /sys/kernel/debug/kvm/408-7/vcpu8
/sys/kernel/debug/kvm/408-7/vcpu22 /sys/kernel/debug/kvm/408-7/vcpu9
But the guest sees CPUs 0-11, the kvm exit/enter events will also show the
above numbers (vcpu 8 for guest CPU 3).
Have the mapping logic look at these files and sort them, and then map the
threads to CPU via them.
Link: https://lore.kernel.org/all/20220504010242.1388192-1-vineethrp@xxxxxxxxxx/
Reported-by: Vineeth Pillai <vineethrp@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
tracecmd/trace-tsync.c | 100 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 99 insertions(+), 1 deletion(-)
diff --git a/tracecmd/trace-tsync.c b/tracecmd/trace-tsync.c
index a96b4e43e0d9..57baff399bd3 100644
--- a/tracecmd/trace-tsync.c
+++ b/tracecmd/trace-tsync.c
@@ -16,14 +16,105 @@ struct trace_mapping {
struct tep_format_field *common_pid;
int *pids;
int *map;
+ int *vcpu;
int max_cpus;
};
+static int cmp_tmap_vcpu(const void *A, const void *B)
+{
+ const int *a = A;
+ const int *b = B;
+
+ if (*a < *b)
+ return -1;
+ return *a > *b;
+}
+
+static int map_kvm_vcpus(int guest_pid, struct trace_mapping *tmap)
+{
+ struct dirent *entry;
+ const char *debugfs;
+ char *vm_dir_str = NULL;
+ char *pid_file = NULL;
+ char *kvm_dir;
+ int pid_file_len;
+ bool found = false;
+ DIR *dir;
+ int ret = -1;
+ int i;
+
+ tmap->vcpu = malloc(sizeof(*tmap->vcpu) * tmap->max_cpus);
+ if (!tmap->vcpu)
+ return -1;
+
+ memset(tmap->vcpu, -1, sizeof(*tmap->vcpu) * tmap->max_cpus);
+
+ debugfs = tracefs_debug_dir();
+ if (!debugfs)
+ return -1;
+
+ if (asprintf(&kvm_dir, "%s/kvm", debugfs) < 0)
+ return -1;
+
+ dir = opendir(kvm_dir);
+ if (!dir)
+ goto out;
+
+ if (asprintf(&pid_file, "%d-", guest_pid) <= 0)
+ goto out;
+
+ pid_file_len = strlen(pid_file);
+
+ while ((entry = readdir(dir))) {
+ if (entry->d_type != DT_DIR ||
+ strncmp(entry->d_name, pid_file, pid_file_len) != 0)
+ continue;
+ if (asprintf(&vm_dir_str, "%s/%s", kvm_dir, entry->d_name) < 0)
+ goto out;
+ found = true;
+ break;
+ }
+ if (!found)
+ goto out;
+
+ closedir(dir);
+ dir = opendir(vm_dir_str);
+ if (!dir)
+ goto out;
+ i = 0;
+ while ((entry = readdir(dir))) {
+ if (entry->d_type != DT_DIR ||
+ strncmp(entry->d_name, "vcpu", 4))
+ continue;
+ if (i == tmap->max_cpus)
+ goto out;
+ tmap->vcpu[i] = strtol(entry->d_name + 4, NULL, 10);
+ i++;
+ }
+
+ if (i < tmap->max_cpus)
+ goto out;
+
+ qsort(tmap->vcpu, tmap->max_cpus, sizeof(*tmap->vcpu), cmp_tmap_vcpu);
+
+ ret = 0;
+
+ out:
+ if (dir)
+ closedir(dir);
+ free(vm_dir_str);
+ free(pid_file);
+ free(kvm_dir);
+
+ return ret;
+}
+
static int map_vcpus(struct tep_event *event, struct tep_record *record,
int cpu, void *context)
{
struct trace_mapping *tmap = context;
unsigned long long val;
+ int *vcpu;
int type;
int pid;
int ret;
@@ -53,10 +144,13 @@ static int map_vcpus(struct tep_event *event, struct tep_record *record,
cpu = (int)val;
+ vcpu = bsearch(&cpu, tmap->vcpu, tmap->max_cpus, sizeof(cpu), cmp_tmap_vcpu);
/* Sanity check, warn? */
- if (cpu >= tmap->max_cpus)
+ if (!vcpu)
return 0;
+ cpu = vcpu - tmap->vcpu;
+
/* Already have this one? Should we check if it is the same? */
if (tmap->map[cpu] >= 0)
return 0;
@@ -123,6 +217,10 @@ static void stop_mapping_vcpus(int cpu_count, struct trace_guest *guest)
if (!tmap.map)
return;
+ /* Check if the kvm vcpu mappings are the same */
+ if (map_kvm_vcpus(guest->pid, &tmap) < 0)
+ goto out;
+
for (i = 0; i < tmap.max_cpus; i++)
tmap.map[i] = -1;
--
2.35.1
|