[libvirt] [PATCH] cpustat: fix regression when cpus are offline

[Eric Blake]

It turns out that the cpuacct results properly account for offline
cpus, and always returns results for every possible cpu, not just
the online ones.  So there is no need to check the map of online
cpus in the first place, merely only a need to know the maximum
possible cpu.  Meanwhile, virNodeGetCPUBitmap had a subtle change
from returning the maximum id to instead returning the width of
the bitmap (one larger than the maximum id), which made this code
encounter some off-by-one logic leading to bad error messages when
a cpu was offline:

$ virsh cpu-stats dom
error: Failed to virDomainGetCPUStats()

error: An error occurred, but the cause is unknown

* src/qemu/qemu_driver.c (qemuDomainGetPercpuStats): Drop
pointless check for cpumap changes, and use correct number of
cpus.
---

Fixes the regression noticed here:
https://www.redhat.com/archives/libvir-list/2012-October/msg01508.html

 src/qemu/qemu_driver.c | 26 +++-----------------------
 1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 18be7d9..f817319 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -13597,7 +13597,6 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
                          unsigned int ncpus)
 {
     virBitmapPtr map = NULL;
-    virBitmapPtr map2 = NULL;
     int rv = -1;
     int i, id, max_id;
     char *pos;
@@ -13609,7 +13608,6 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
     virTypedParameterPtr ent;
     int param_idx;
     unsigned long long cpu_time;
-    bool result;

     /* return the number of supported params */
     if (nparams == 0 && ncpus != 0)
@@ -13621,7 +13619,7 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
         return rv;

     if (ncpus == 0) { /* returns max cpu ID */
-        rv = max_id + 1;
+        rv = max_id;
         goto cleanup;
     }

@@ -13648,11 +13646,7 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
         id = start_cpu + ncpus - 1;

     for (i = 0; i <= id; i++) {
-        if (virBitmapGetBit(map, i, &result) < 0)
-            goto cleanup;
-        if (!result) {
-            cpu_time = 0;
-        } else if (virStrToLong_ull(pos, &pos, 10, &cpu_time) < 0) {
+        if (virStrToLong_ull(pos, &pos, 10, &cpu_time) < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                            _("cpuacct parse error"));
             goto cleanup;
@@ -13680,22 +13674,9 @@ qemuDomainGetPercpuStats(virDomainPtr domain,
     if (getSumVcpuPercpuStats(group, priv->nvcpupids, sum_cpu_time, n) < 0)
         goto cleanup;

-    /* Check that the mapping of online cpus didn't change mid-parse.  */
-    map2 = nodeGetCPUBitmap(domain->conn, &max_id);
-    if (!map2 || !virBitmapEqual(map, map2)) {
-        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
-                       _("the set of online cpus changed while reading"));
-        goto cleanup;
-    }
-
     sum_cpu_pos = sum_cpu_time;
     for (i = 0; i <= id; i++) {
-        if (virBitmapGetBit(map, i, &result) < 0)
-            goto cleanup;
-        if (!result)
-            cpu_time = 0;
-        else
-            cpu_time = *(sum_cpu_pos++);
+        cpu_time = *(sum_cpu_pos++);
         if (i < start_cpu)
             continue;
         if (virTypedParameterAssign(&params[(i - start_cpu) * nparams +
@@ -13711,7 +13692,6 @@ cleanup:
     VIR_FREE(sum_cpu_time);
     VIR_FREE(buf);
     virBitmapFree(map);
-    virBitmapFree(map2);
     return rv;
 }

-- 
1.7.11.7