From ec03aa23ac417797f9b53d51b6f999f5e966f9d7 Mon Sep 17 00:00:00 2001
Message-Id: <ec03aa23ac417797f9b53d51b6f999f5e966f9d7@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Mon, 16 Jan 2023 12:46:09 +0100
Subject: [PATCH] qemu: Provide virDomainGetCPUStats() implementation for
 session connection

We have virDomainGetCPUStats() API which offers querying
statistics on host CPU usage by given guest. And it works in two
modes: getting overall stats (@start_cpu == -1, @ncpus == 1) or
getting per host CPU usage.

For the QEMU driver it is implemented by looking into values
stored in corresponding cpuacct CGroup controller. Well, this
works for system instances, where libvirt has permissions to
create CGroups and place QEMU process into them. But it does not
fly for session connection, where no CGroups are set up.

Fortunately, we can do something similar to v8.8.0-rc1~95 and use
virProcessGetStatInfo() to fill the overall stats. Unfortunately,
I haven't found any source of per host CPU usage, so we just
continue throwing an error in that case.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
(cherry picked from commit 8865c42771600a40eddf40663f73b458423059a4)
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2148266
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 src/qemu/qemu_driver.c | 52 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index c576c601ad..0603af6a35 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16009,6 +16009,50 @@ qemuDomainGetMetadata(virDomainPtr dom,
     return ret;
 }
 
+#define QEMU_CPU_STATS_PROC_TOTAL 3
+
+static int
+qemuDomainGetCPUStatsProc(virDomainObj *vm,
+                          virTypedParameterPtr params,
+                          unsigned int nparams)
+{
+    unsigned long long cpuTime = 0;
+    unsigned long long userTime = 0;
+    unsigned long long sysTime = 0;
+
+    if (nparams == 0) {
+        /* return supported number of params */
+        return QEMU_CPU_STATS_PROC_TOTAL;
+    }
+
+    if (virProcessGetStatInfo(&cpuTime, &userTime, &sysTime,
+                              NULL, NULL, vm->pid, 0) < 0) {
+        virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                       _("cannot read cputime for domain"));
+        return -1;
+    }
+
+    if (virTypedParameterAssign(&params[0], VIR_DOMAIN_CPU_STATS_CPUTIME,
+                                VIR_TYPED_PARAM_ULLONG, cpuTime) < 0)
+        return -1;
+
+    if (nparams > 1 &&
+        virTypedParameterAssign(&params[1], VIR_DOMAIN_CPU_STATS_USERTIME,
+                                VIR_TYPED_PARAM_ULLONG, userTime) < 0)
+        return -1;
+
+    if (nparams > 2 &&
+        virTypedParameterAssign(&params[2], VIR_DOMAIN_CPU_STATS_SYSTEMTIME,
+                                VIR_TYPED_PARAM_ULLONG, sysTime) < 0)
+        return -1;
+
+    if (nparams > 3)
+        nparams = 3;
+
+    return nparams;
+}
+
+#undef QEMU_CPU_STATS_PROC_TOTAL
 
 static int
 qemuDomainGetCPUStats(virDomainPtr domain,
@@ -16037,8 +16081,12 @@ qemuDomainGetCPUStats(virDomainPtr domain,
         goto cleanup;
 
     if (!virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_CPUACCT)) {
-        virReportError(VIR_ERR_OPERATION_INVALID,
-                       "%s", _("cgroup CPUACCT controller is not mounted"));
+        if (start_cpu == -1) {
+            ret = qemuDomainGetCPUStatsProc(vm, params, nparams);
+        } else {
+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                           _("cgroup CPUACCT controller is not mounted"));
+        }
         goto cleanup;
     }
 
-- 
2.39.1