[PATCH] qga: add command 'guest-get-cpustats'

[zhenwei pi]

A vCPU thread always reaches 100% utilization when:
- guest uses idle=poll
- disable HLT vm-exit
- enable MWAIT

Add new guest agent command 'guest-get-cpustats' to get guest CPU
statistics, we can know the guest workload and how busy the CPU is.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 qga/commands-posix.c | 72 ++++++++++++++++++++++++++++++++++++++++++++
 qga/commands-win32.c |  6 ++++
 qga/qapi-schema.json | 49 ++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 0469dc409d..2847023876 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -2893,6 +2893,73 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error 
**errp)
     return guest_get_diskstats(errp);
 }
 
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    GuestCpuStatsList *head = NULL, **tail = &head;
+    const char *cpustats = "/proc/stat";
+    FILE *fp;
+    size_t n;
+    char *line = NULL;
+
+    fp = fopen(cpustats, "r");
+    if (fp  == NULL) {
+        error_setg_errno(errp, errno, "open(\"%s\")", cpustats);
+        return NULL;
+    }
+
+    while (getline(&line, &n, fp) != -1) {
+        GuestCpuStats *cpustat = NULL;
+        int i;
+        unsigned long user, system, idle, iowait, irq, softirq, steal, guest;
+        unsigned long nice, guest_nice;
+        char name[64];
+
+        i = sscanf(line, "%s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
+                   name, &user, &nice, &system, &idle, &iowait, &irq, &softirq,
+                   &steal, &guest, &guest_nice);
+
+        /* drop "cpu 1 2 3 ...", get "cpuX 1 2 3 ..." only */
+        if (strncmp(name, "cpu", 3) || (name[3] == '\0')) {
+            continue;
+        }
+
+        cpustat = g_new0(GuestCpuStats, 1);
+        cpustat->cpu = atoi(&name[3]);
+        cpustat->has_user = true;
+        cpustat->user = user * 10;
+        cpustat->has_system = true;
+        cpustat->system = system * 10;
+        cpustat->has_idle = true;
+        cpustat->idle = idle * 10;
+
+        /* Linux version >= 2.6 */
+        if (i > 5) {
+            cpustat->has_iowait = true;
+            cpustat->iowait = iowait * 10;
+            cpustat->has_irq = true;
+            cpustat->irq = irq * 10;
+            cpustat->has_softirq = true;
+            cpustat->softirq = softirq * 10;
+        }
+
+        if (i > 8) {
+            cpustat->has_steal = true;
+            cpustat->steal = steal * 10;
+        }
+
+        if (i > 9) {
+            cpustat->has_guest = true;
+            cpustat->guest = guest * 10;
+        }
+
+        QAPI_LIST_APPEND(tail, cpustat);
+    }
+
+    free(line);
+    fclose(fp);
+    return head;
+}
+
 #else /* defined(__linux__) */
 
 void qmp_guest_suspend_disk(Error **errp)
@@ -3247,6 +3314,11 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error 
**errp)
     return NULL;
 }
 
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
 
 #endif /* CONFIG_FSFREEZE */
 
diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 36f94c0f9c..7ed7664715 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -2543,3 +2543,9 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error 
**errp)
     error_setg(errp, QERR_UNSUPPORTED);
     return NULL;
 }
+
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 9fa20e791b..4859c887b2 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -1576,3 +1576,52 @@
 { 'command': 'guest-get-diskstats',
   'returns': ['GuestDiskStatsInfo']
 }
+
+##
+# @GuestCpuStats:
+#
+# Get statistics of each CPU in millisecond.
+#
+# @cpu: CPU index in guest OS
+#
+# @user: CPU time of user mode
+#
+# @system: CPU time of system mode
+#
+# @idle: CPU time of idle state
+#
+# @iowait: CPU time waiting IO
+#
+# @irq: CPU time of hardware interrupt
+#
+# @softirq: CPU time of soft interrupt
+#
+# @steal: CPU time stolen by host
+#
+# @guest: CPU time of running guest mode
+#
+# Since: 7.1
+##
+{ 'struct': 'GuestCpuStats',
+  'data': {'cpu': 'int',
+           '*user': 'uint64',
+           '*system': 'uint64',
+           '*idle': 'uint64',
+           '*iowait': 'uint64',
+           '*irq': 'uint64',
+           '*softirq': 'uint64',
+           '*steal': 'uint64',
+           '*guest': 'uint64'
+           } }
+
+##
+# @guest-get-cpustats:
+#
+# Retrieve information about CPU stats.
+# Returns: List of CPU stats of guest.
+#
+# Since: 7.1
+##
+{ 'command': 'guest-get-cpustats',
+  'returns': ['GuestCpuStats']
+}
-- 
2.20.1