[Qemu-devel] [PATCH 4/4] target/i386: Don't use x86_cpu_load_def() on "max" CPU model

[Eduardo Habkost]

When commit 0bacd8b3046f ('i386: Don't set CPUClass::cpu_def on
"max" model') removed the CPUClass::cpu_def field, we kept using
the x86_cpu_load_def() helper directly in max_x86_cpu_initfn(),
emulating the previous behavior when CPUClass::cpu_def was set.

However, x86_cpu_load_def() is intended to help initialization of
CPU models from the builtin_x86_defs table, and does lots of
other steps that are not necessary for "max".

One of the things x86_cpu_load_def() do is to set the properties
listed at tcg_default_props/kvm_default_props.  We must not do
that on the "max" CPU model, otherwise under KVM we will
incorrectly report all KVM features as always available, and the
"svm" feature as always unavailable.  The latter caused the bug
reported at:

  https://bugzilla.redhat.com/show_bug.cgi?id=1467599
  ("Unable to start domain: the CPU is incompatible with host CPU:
  Host CPU does not provide required features: svm")

Replace x86_cpu_load_def() with simple object_property_set*()
calls.  In addition to fixing the above bug, this makes the KVM
branch in max_x86_cpu_initfn() very similar to the existing TCG
branch.

Signed-off-by: Eduardo Habkost <address@hidden>
---
 target/i386/cpu.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index e2cd157..62d8021 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1596,15 +1596,21 @@ static void max_x86_cpu_initfn(Object *obj)
     cpu->max_features = true;
 
     if (kvm_enabled()) {
-        X86CPUDefinition host_cpudef = { };
-        uint32_t eax = 0, ebx = 0, ecx = 0, edx = 0;
+        char vendor[CPUID_VENDOR_SZ + 1] = { 0 };
+        char model_id[CPUID_MODEL_ID_SZ + 1] = { 0 };
+        int family, model, stepping;
 
-        host_vendor_fms(host_cpudef.vendor, &host_cpudef.family,
-                        &host_cpudef.model, &host_cpudef.stepping);
+        host_vendor_fms(vendor, &family, &model, &stepping);
 
-        cpu_x86_fill_model_id(host_cpudef.model_id);
+        cpu_x86_fill_model_id(model_id);
 
-        x86_cpu_load_def(cpu, &host_cpudef, &error_abort);
+        object_property_set_str(OBJECT(cpu), vendor, "vendor", &error_abort);
+        object_property_set_int(OBJECT(cpu), family, "family", &error_abort);
+        object_property_set_int(OBJECT(cpu), model, "model", &error_abort);
+        object_property_set_int(OBJECT(cpu), stepping, "stepping",
+                                &error_abort);
+        object_property_set_str(OBJECT(cpu), model_id, "model-id",
+                                &error_abort);
 
         env->cpuid_min_level =
             kvm_arch_get_supported_cpuid(s, 0x0, 0, R_EAX);
-- 
2.9.4