KVM: x86: Move VMX's host_efer to common x86 code

Move host_efer to common x86 code and use it for CPUID's is_efer_nx() to
avoid constantly re-reading the MSR.

No functional change intended.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1271,6 +1271,8 @@ struct kvm_arch_async_pf {
 	bool direct_map;
 };
 
+extern u64 __read_mostly host_efer;
+
 extern struct kvm_x86_ops *kvm_x86_ops;
 extern struct kmem_cache *x86_fpu_cache;
 

arch/x86/kvm/cpuid.c

@@ -134,10 +134,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 
 static int is_efer_nx(void)
 {
-	unsigned long long efer = 0;
-
-	rdmsrl_safe(MSR_EFER, &efer);
-	return efer & EFER_NX;
+	return host_efer & EFER_NX;
 }
 
 static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu)

arch/x86/kvm/vmx/vmx.c

@@ -433,7 +433,6 @@ static const struct kvm_vmx_segment_field {
 	VMX_SEGMENT_FIELD(LDTR),
 };
 
-u64 host_efer;
 static unsigned long host_idt_base;
 
 /*
@@ -7646,8 +7645,6 @@ static __init int hardware_setup(void)
 	struct desc_ptr dt;
 	int r, i, ept_lpage_level;
 
-	rdmsrl_safe(MSR_EFER, &host_efer);
-
 	store_idt(&dt);
 	host_idt_base = dt.address;
 

arch/x86/kvm/vmx/vmx.h

@@ -12,7 +12,6 @@
 #include "vmcs.h"
 
 extern const u32 vmx_msr_index[];
-extern u64 host_efer;
 
 extern u32 get_umwait_control_msr(void);
 

arch/x86/kvm/x86.c

@@ -186,6 +186,9 @@ static struct kvm_shared_msrs __percpu *shared_msrs;
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU)
 
+u64 __read_mostly host_efer;
+EXPORT_SYMBOL_GPL(host_efer);
+
 static u64 __read_mostly host_xss;
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
@@ -9612,6 +9615,8 @@ int kvm_arch_hardware_setup(void)
 {
 	int r;
 
+	rdmsrl_safe(MSR_EFER, &host_efer);
+
 	r = kvm_x86_ops->hardware_setup();
 	if (r != 0)
 		return r;