[PATCH] util: virhostcpu: Fail when fetching CPU Stats for invalid cpu

["Mauro S. M. Rodrigues" <maurosr@xxxxxxxxxxxxxxxxxx>]

virHostCPUGetStatsLinux walks through every cpu in /proc/stat until it
finds cpu%cpuNum that matches with the requested cpu.
If none is found it logs the error but it should return -1, instead of 0.
Otherwise virsh nodecpustats --cpu <invalid cpu number> and API bindings
don't fail properly, printing a blank line instead of an error message.

This patch also includes an additional test for virhostcputest to avoid
this regression to happen again in the future.

Reported-by: Satheesh Rajendran <satheera@xxxxxxxxxx>
Signed-off-by: Mauro S. M. Rodrigues <maurosr@xxxxxxxxxxxxxxxxxx>
---
 src/util/virhostcpu.c  | 2 +-
 tests/virhostcputest.c | 9 ++++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c
index 81293eea8c..20c8d0ce6c 100644
--- a/src/util/virhostcpu.c
+++ b/src/util/virhostcpu.c
@@ -847,7 +847,7 @@ virHostCPUGetStatsLinux(FILE *procstat,
                         _("Invalid cpuNum in %s"),
                         __FUNCTION__);
 
-    return 0;
+    return -1;
 }
 
 
diff --git a/tests/virhostcputest.c b/tests/virhostcputest.c
index 7865b61578..2f569d8bd4 100644
--- a/tests/virhostcputest.c
+++ b/tests/virhostcputest.c
@@ -258,14 +258,17 @@ mymain(void)
         if (virTestRun(nodeData[i].testName, linuxTestHostCPU, &nodeData[i]) != 0)
             ret = -1;
 
-# define DO_TEST_CPU_STATS(name, ncpus) \
+# define DO_TEST_CPU_STATS(name, ncpus, shouldFail) \
     do { \
         static struct nodeCPUStatsData data = { name, ncpus }; \
-        if (virTestRun("CPU stats " name, linuxTestNodeCPUStats, &data) < 0) \
+        if ((virTestRun("CPU stats " name, \
+			linuxTestNodeCPUStats, \
+			&data) < 0) != shouldFail) \
             ret = -1; \
     } while (0)
 
-    DO_TEST_CPU_STATS("24cpu", 24);
+    DO_TEST_CPU_STATS("24cpu", 24, false);
+    DO_TEST_CPU_STATS("24cpu", 25, true);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
-- 
2.24.1