[COMMIT master] Fix KVMs GET_SUPPORTED_CPUID feature usage

[Avi Kivity]

From: Andre Przywara <andre.przyw...@amd.com>

If we want to trim the user provided CPUID bits for KVM to be not greater
than that of the host, we should

a) not remove the bits _after_ we sent them to the kernel  and
b) not do the bitmangling on the original values while sending a copy

This fixes the masking of features that are not present on the host and
helps to use -cpu host.

Signed-off-by: Andre Przywara <andre.przyw...@amd.com>
Signed-off-by: Avi Kivity <a...@redhat.com>

diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index 1eb147e..a5c72e9 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -1191,7 +1191,6 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
 
     qemu_kvm_load_lapic(cenv);
 
-    copy = *cenv;
 
 #ifdef KVM_CPUID_SIGNATURE
     /* Paravirtualization CPUIDs */
@@ -1210,6 +1209,17 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
     pv_ent->eax = get_para_features(kvm_context);
 #endif
 
+    kvm_trim_features(&cenv->cpuid_features,
+                      kvm_arch_get_supported_cpuid(cenv, 1, R_EDX));
+    kvm_trim_features(&cenv->cpuid_ext_features,
+                      kvm_arch_get_supported_cpuid(cenv, 1, R_ECX));
+    kvm_trim_features(&cenv->cpuid_ext2_features,
+                      kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_EDX));
+    kvm_trim_features(&cenv->cpuid_ext3_features,
+                      kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_ECX));
+
+    copy = *cenv;
+
     copy.regs[R_EAX] = 0;
     qemu_kvm_cpuid_on_env(&copy);
     limit = copy.regs[R_EAX];
@@ -1244,15 +1254,6 @@ int kvm_arch_qemu_init_env(CPUState *cenv)
 
     kvm_setup_cpuid2(cenv->kvm_cpu_state.vcpu_ctx, cpuid_nent, cpuid_ent);
 
-    kvm_trim_features(&cenv->cpuid_features,
-                      kvm_arch_get_supported_cpuid(cenv, 1, R_EDX));
-    kvm_trim_features(&cenv->cpuid_ext_features,
-                      kvm_arch_get_supported_cpuid(cenv, 1, R_ECX));
-    kvm_trim_features(&cenv->cpuid_ext2_features,
-                      kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_EDX));
-    kvm_trim_features(&cenv->cpuid_ext3_features,
-                      kvm_arch_get_supported_cpuid(cenv, 0x80000001, R_ECX));
-
     return 0;
 }
 
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