qga: Correct loop count in qmp_guest_get_vcpus()

The guest-get-vcpus returns incorrect vcpu info in case we hotunplug vcpus(not
the last one).
e.g.:
A VM has 4 VCPUs: cpu0 + 3 hotunpluggable online vcpus(cpu1, cpu2 and cpu3).
Hotunplug cpu2,  Now only cpu0, cpu1 and cpu3 are present & online.

./qmp-shell /tmp/qmp-monitor.sock
(QEMU) query-hotpluggable-cpus
{"return": [
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 3}, "vcpus-count": 1,
 "qom-path": "/machine/peripheral/cpu3", "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 2}, "vcpus-count": 1,
 "qom-path": "/machine/peripheral/cpu2", "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 1}, "vcpus-count": 1,
 "qom-path": "/machine/peripheral/cpu1", "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 0}, "vcpus-count": 1,
 "qom-path": "/machine/unattached/device[0]", "type": "host-x86_64-cpu"}
]}

(QEMU) device_del id=cpu2
{"return": {}}

(QEMU) query-hotpluggable-cpus
{"return": [
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 3}, "vcpus-count": 1,
 "qom-path": "/machine/peripheral/cpu3", "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 2}, "vcpus-count": 1,
 "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 1}, "vcpus-count": 1,
 "qom-path": "/machine/peripheral/cpu1", "type": "host-x86_64-cpu"},
{"props": {"core-id": 0, "thread-id": 0, "socket-id": 0}, "vcpus-count": 1,
 "qom-path": "/machine/unattached/device[0]", "type": "host-x86_64-cpu"}
]}

Before:
./qmp-shell -N /tmp/qmp-ga.sock
Welcome to the QMP low-level shell!
Connected
(QEMU) guest-get-vcpus
{"return": [
{"online": true, "can-offline": false, "logical-id": 0},
{"online": true, "can-offline": true, "logical-id": 1}]}

After:
./qmp-shell -N /tmp/qmp-ga.sock
Welcome to the QMP low-level shell!
Connected
(QEMU) guest-get-vcpus
{"return": [
{"online": true, "can-offline": false, "logical-id": 0},
{"online": true, "can-offline": true, "logical-id": 1},
{"online": true, "can-offline": true, "logical-id": 3}]}

Signed-off-by: Lin Ma <lma@suse.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
*fix build breakage by using PRId64 for sscanf
Signed-off-by: Michael Roth <michael.roth@amd.com>

1 files changed, 14 insertions, 29 deletions

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 3f18df1bb6..665735fd09 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -2370,24 +2370,6 @@ error:
     return NULL;
 }
 
-#define SYSCONF_EXACT(name, errp) sysconf_exact((name), #name, (errp))
-
-static long sysconf_exact(int name, const char *name_str, Error **errp)
-{
-    long ret;
-
-    errno = 0;
-    ret = sysconf(name);
-    if (ret == -1) {
-        if (errno == 0) {
-            error_setg(errp, "sysconf(%s): value indefinite", name_str);
-        } else {
-            error_setg_errno(errp, errno, "sysconf(%s)", name_str);
-        }
-    }
-    return ret;
-}
-
 /* Transfer online/offline status between @vcpu and the guest system.
  *
  * On input either @errp or *@errp must be NULL.
@@ -2458,30 +2440,33 @@ static void transfer_vcpu(GuestLogicalProcessor *vcpu, bool sys2vcpu,
 
 GuestLogicalProcessorList *qmp_guest_get_vcpus(Error **errp)
 {
-    int64_t current;
     GuestLogicalProcessorList *head, **tail;
-    long sc_max;
+    const char *cpu_dir = "/sys/devices/system/cpu";
+    const gchar *line;
+    g_autoptr(GDir) cpu_gdir = NULL;
     Error *local_err = NULL;
 
-    current = 0;
     head = NULL;
     tail = &head;
-    sc_max = SYSCONF_EXACT(_SC_NPROCESSORS_CONF, &local_err);
+    cpu_gdir = g_dir_open(cpu_dir, 0, NULL);
 
-    while (local_err == NULL && current < sc_max) {
-        GuestLogicalProcessor *vcpu;
-        int64_t id = current++;
-        char *path = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
-                                     id);
+    if (cpu_gdir == NULL) {
+        error_setg_errno(errp, errno, "failed to list entries: %s", cpu_dir);
+        return NULL;
+    }
 
-        if (g_file_test(path, G_FILE_TEST_EXISTS)) {
+    while (local_err == NULL && (line = g_dir_read_name(cpu_gdir)) != NULL) {
+        GuestLogicalProcessor *vcpu;
+        int64_t id;
+        if (sscanf(line, "cpu%" PRId64, &id)) {
+            g_autofree char *path = g_strdup_printf("/sys/devices/system/cpu/"
+                                                    "cpu%" PRId64 "/", id);
             vcpu = g_malloc0(sizeof *vcpu);
             vcpu->logical_id = id;
             vcpu->has_can_offline = true; /* lolspeak ftw */
             transfer_vcpu(vcpu, true, path, &local_err);
             QAPI_LIST_APPEND(tail, vcpu);
         }
-        g_free(path);
     }
 
     if (local_err == NULL) {