remove CPUID host hacks

KVM provides an in-kernel feature to disable CPUID bits that are not
present in the current host. So there is no need here to duplicate this
work. Additionally allows 3DNow! on capable processors, since the
restriction seems to apply to QEMU/TCG only.
Signed-off-by: NAndre Przywara <andre.przywara@amd.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

target-i386/helper.c

@@ -1643,28 +1643,11 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         *edx = env->cpuid_ext2_features;
 
         if (kvm_enabled()) {
-            uint32_t h_eax, h_edx;
-
-            host_cpuid(index, 0, &h_eax, NULL, NULL, &h_edx);
-
-            /* disable CPU features that the host does not support */
-
-            /* long mode */
-            if ((h_edx & 0x20000000) == 0 /* || !lm_capable_kernel */)
-                *edx &= ~0x20000000;
-            /* syscall */
-            if ((h_edx & 0x00000800) == 0)
-                *edx &= ~0x00000800;
-            /* nx */
-            if ((h_edx & 0x00100000) == 0)
-                *edx &= ~0x00100000;
-
-            /* disable CPU features that KVM cannot support */
-
-            /* svm */
-            *ecx &= ~4UL;
-            /* 3dnow */
-            *edx &= ~0xc0000000;
+            /* Nested SVM not yet supported in KVM */
+            *ecx &= ~CPUID_EXT3_SVM;
+        } else {
+            /* AMD 3DNow! is not supported in QEMU */
+            *edx &= ~(CPUID_EXT2_3DNOW | CPUID_EXT2_3DNOWEXT);
         }
         break;
     case 0x80000002: