x86/kvm/vmx: Use native read/write_cr2()

read/write_cr2() go throuh the paravirt XXL indirection, but nested VMX in
a XEN_PV guest is not supported.

Use the native variants.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <20200708195322.344731916@linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -6686,13 +6686,13 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
 	else if (static_branch_unlikely(&mds_user_clear))
 		mds_clear_cpu_buffers();
 
-	if (vcpu->arch.cr2 != read_cr2())
-		write_cr2(vcpu->arch.cr2);
+	if (vcpu->arch.cr2 != native_read_cr2())
+		native_write_cr2(vcpu->arch.cr2);
 
 	vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
 				   vmx->loaded_vmcs->launched);
 
-	vcpu->arch.cr2 = read_cr2();
+	vcpu->arch.cr2 = native_read_cr2();
 
 	/*
 	 * VMEXIT disables interrupts (host state), but tracing and lockdep