[libvirt] [PATCH 1/2] qemu: Invert condition nesting in qemuDomainDefValidate()

[Andrea Bolognani]

While at the moment we're only performing a single check that is
connected to vCPU hotplugging, we're going to introduce a second
one soon. Move the topology check underneath the capability check
to make that easier; as a bonus, doing so allows us to reduce the
scope of the 'topologycpus' variable.

Signed-off-by: Andrea Bolognani <abologna at redhat.com>
---
 src/qemu/qemu_domain.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 74b82450b..e93333669 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -3299,7 +3299,6 @@ qemuDomainDefValidate(const virDomainDef *def,
 {
     virQEMUDriverPtr driver = opaque;
     virQEMUCapsPtr qemuCaps = NULL;
-    unsigned int topologycpus;
     int ret = -1;
 
     if (!(qemuCaps = virQEMUCapsCacheLookup(driver->qemuCapsCache,
@@ -3359,11 +3358,15 @@ qemuDomainDefValidate(const virDomainDef *def,
         }
     }
 
-    /* qemu as of 2.5.0 rejects SMP topologies that don't match the cpu count */
-    if (virDomainDefGetVcpusTopology(def, &topologycpus) == 0 &&
-        topologycpus != virDomainDefGetVcpusMax(def)) {
-        /* presence of query-hotpluggable-cpus should be a good enough witness */
-        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS)) {
+    /* QEMU 2.7 (detected via the availability of query-hotpluggable-cpus)
+     * enforces stricter rules than previous versions when it comes to guest
+     * CPU topology. Verify known constraints are respected */
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS)) {
+        unsigned int topologycpus;
+
+        /* Max vCPU count and overall vCPU topology must agree */
+        if (virDomainDefGetVcpusTopology(def, &topologycpus) == 0 &&
+            topologycpus != virDomainDefGetVcpusMax(def)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("CPU topology doesn't match maximum vcpu count"));
             goto cleanup;
-- 
2.14.3