From 5ed97c22865c86ccca3802d24c9893dd1109ab34 Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Tue, 17 Mar 2020 18:33:31 +0100
Subject: [PATCH] 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>
---
 src/qemu/qemu_hotplug.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 47069be900..a76df64a7b 100644
--- 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,
-- 
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