Modify virCPUarmCompare in cpu_arm.c to perform compare action.
This patch only adds host to host CPU compare, the rest cases
remains the same. This is useful for source and destination host
compare during migrations to avoid migration between different
CPU models that have different CPU freatures.

Signed-off-by: Zhenyu Zheng <zheng.zhenyu@outlook.com>
---
 src/cpu/cpu_arm.c | 43 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/src/cpu/cpu_arm.c b/src/cpu/cpu_arm.c
index 939a3b8390..b420b14e86 100644
--- a/src/cpu/cpu_arm.c
+++ b/src/cpu/cpu_arm.c
@@ -463,11 +463,46 @@ virCPUarmBaseline(virCPUDefPtr *cpus,
 }

 static virCPUCompareResult
-virCPUarmCompare(virCPUDefPtr host G_GNUC_UNUSED,
-                 virCPUDefPtr cpu G_GNUC_UNUSED,
-                 bool failMessages G_GNUC_UNUSED)
+virCPUarmCompare(virCPUDefPtr host,
+                 virCPUDefPtr cpu,
+                 bool failIncompatible
+)
 {
-    return VIR_CPU_COMPARE_IDENTICAL;
+    virCPUCompareResult ret = VIR_CPU_COMPARE_IDENTICAL;
+
+    /* Only support host to host CPU compare for ARM*/
+    if (cpu->type != VIR_CPU_TYPE_HOST)
+        return ret;
+
+    if (!host || !host->model) {
+        if (failIncompatible) {
+            virReportError(VIR_ERR_CPU_INCOMPATIBLE, "%s",
+                           _("unknown host CPU"));
+            ret = VIR_CPU_COMPARE_ERROR;
+        } else {
+            VIR_WARN("unknown host CPU");
+            ret = VIR_CPU_COMPARE_INCOMPATIBLE;
+        }
+        return ret;
+    }
+
+    /* Compare vendor and model to check if CPUs are identical */
+    if (STRNEQ(host->vendor, cpu->vendor) ||
+        STRNEQ(host->model, cpu->model)) {
+        VIR_DEBUG("Host CPU model does not match required CPU model %s",
+                  cpu->model);
+
+        if (failIncompatible) {
+            ret = VIR_CPU_COMPARE_ERROR;
+            virReportError(VIR_ERR_CPU_INCOMPATIBLE,
+                           _("Host CPU model does not match required CPU model %s"),
+                           cpu->model);
+        } else {
+            ret = VIR_CPU_COMPARE_INCOMPATIBLE;
+        }
+    }
+
+    return ret;
 }

 static int
--
2.20.1