[libvirt] [PATCH] cpuBaseline: Detect empty set of common features

[Jiri Denemark]

In case the set of CPUs has no features in common, report incompatible
CPUs instead of returning the simplest CPU model with all features
disabled.
---
 src/cpu/cpu_x86.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index 30a2db6..0266ce9 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -233,6 +233,26 @@ x86DataSubtract(union cpuData *data1,
 }
 
 
+static bool
+x86DataIsEmpty(union cpuData *data)
+{
+    struct cpuX86cpuid zero = { 0, 0, 0, 0, 0 };
+    unsigned int i;
+
+    for (i = 0; i < data->x86.basic_len; i++) {
+        if (!x86cpuidMatch(data->x86.basic + i, &zero))
+            return false;
+    }
+
+    for (i = 0; i < data->x86.extended_len; i++) {
+        if (!x86cpuidMatch(data->x86.extended + i, &zero))
+            return false;
+    }
+
+    return true;
+}
+
+
 static union cpuData *
 x86DataFromModel(const struct x86_model *model)
 {
@@ -1363,6 +1383,12 @@ x86Baseline(virCPUDefPtr *cpus,
     if (!(data = x86DataFromModel(base_model)))
         goto no_memory;
 
+    if (x86DataIsEmpty(data)) {
+        virCPUReportError(VIR_ERR_OPERATION_FAILED,
+                "%s", _("CPUs are incompatible"));
+        goto error;
+    }
+
     if (x86Decode(cpu, data, models, nmodels, NULL) < 0)
         goto error;
 
-- 
1.7.1.1