qemuDomainVcpuValidateConfig: Properly initialize 'firstcpu' variable

The loop which checks whether the vcpus are in proper configuration for
the requested hot(un)plug skips the first modified vcpu. This means
that 'firstvcpu' which is used to print the error message in case the
configuration is not suitable would never point to the first modified
vcpu.

In cases such as:

  <vcpu placement='auto' current='5'>8</vcpu>
  <vcpus>
    <vcpu id='0' enabled='yes' hotpluggable='no'/>
    <vcpu id='1' enabled='yes' hotpluggable='no'/>
    <vcpu id='2' enabled='yes' hotpluggable='no'/>
    <vcpu id='3' enabled='yes' hotpluggable='no'/>
    <vcpu id='4' enabled='yes' hotpluggable='no'/>
    <vcpu id='5' enabled='no' hotpluggable='yes'/>
    <vcpu id='6' enabled='no' hotpluggable='yes'/>
    <vcpu id='7' enabled='no' hotpluggable='yes'/>
  </vcpus>

 # virsh setvcpu --config --disable  upstream 1
 error: invalid argument: vcpu '-1' can't be modified as it is followed by non-hotpluggable online vcpus

After this fix the proper vcpu is reported in the error message:

 # virsh setvcpu --config --disable  upstream 1
 error: invalid argument: vcpu '1' can't be modified as it is followed by non-hotpluggable online vcpu

https://bugzilla.redhat.com/show_bug.cgi?id=1611061

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 47069be90072f6e0d9fb51b4dfe090296fab3fdf..a76df64a7b913ff9720df0b9e280d5372254becc 100644 (file)
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -6478,18 +6478,16 @@ qemuDomainVcpuValidateConfig(virDomainDefPtr def,
         return -1;
     }
 
+    firstvcpu = virBitmapNextSetBit(map, -1);
+
     /* non-hotpluggable vcpus need to stay clustered starting from vcpu 0 */
-    for (next = virBitmapNextSetBit(map, -1) + 1; next < maxvcpus; next++) {
+    for (next = firstvcpu + 1; next < maxvcpus; next++) {
         if (!(vcpu = virDomainDefGetVcpu(def, next)))
             continue;
 
         /* skip vcpus being modified */
-        if (virBitmapIsBitSet(map, next)) {
-            if (firstvcpu < 0)
-                firstvcpu = next;
-
+        if (virBitmapIsBitSet(map, next))
             continue;
-        }
 
         if (vcpu->online && vcpu->hotpluggable == VIR_TRISTATE_BOOL_NO) {
             virReportError(VIR_ERR_INVALID_ARG,