[Qemu-devel] [PATCH v13 4/5] i386: Verify and enable topoext feature if supported

[Babu Moger]

If the CPU model supports topoext feature, enabled the
feature automatically if it can be supported.

Signed-off-by: Babu Moger <address@hidden>
---
 target/i386/cpu.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4dd9a82..88bc73d 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -4763,6 +4763,33 @@ static int x86_cpu_filter_features(X86CPU *cpu)
 #define IS_AMD_CPU(env) ((env)->cpuid_vendor1 == CPUID_VENDOR_AMD_1 && \
                          (env)->cpuid_vendor2 == CPUID_VENDOR_AMD_2 && \
                          (env)->cpuid_vendor3 == CPUID_VENDOR_AMD_3)
+/*
+ * Check if we can support this topology
+ * Fail if number of cores are beyond the supported config
+ * or nr_threads is more than 2
+ */
+static int topology_supports_topoext(int nr_cores, int nr_threads,
+            Error **errp)
+{
+    if (nr_cores > (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET)) {
+        error_setg(errp, "TOPOEXT unsupported with %d cores per socket",
+                   nr_cores);
+        error_append_hint(errp, "TOPOEXT supports only up to %d cores per"
+                          " socket\n",
+                          (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET));
+        return false;
+    }
+
+    if (nr_threads > 2) {
+        error_setg(errp, "TOPOEXT unsupported with %d threads per core",
+                   nr_threads);
+        error_append_hint(errp, "TOPOEXT supports only up to 2 threads"
+                          " per core\n");
+        return false;
+    }
+    return true;
+}
+
 static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
 {
     CPUState *cs = CPU(dev);
@@ -4953,6 +4980,19 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
**errp)
 
     qemu_init_vcpu(cs);
 
+    if (cpu->auto_topoext &&
+        !(env->user_features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT)) {
+        if (cs->nr_cores <= (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET) &&
+            (cs->nr_threads <= 2)) {
+            env->features[FEAT_8000_0001_ECX] |= CPUID_EXT3_TOPOEXT;
+        }
+    }
+
+    if ((env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) &&
+        !topology_supports_topoext(cs->nr_cores, cs->nr_threads, errp)) {
+        return;
+    }
+
     /* Only Intel CPUs support hyperthreading. Even though QEMU fixes this
      * issue by adjusting CPUID_0000_0001_EBX and CPUID_8000_0008_ECX
      * based on inputs (sockets,cores,threads), it is still better to gives
-- 
1.8.3.1