x86/xen: add CONFIG_XEN_PV to Kconfig

All code to support Xen PV will get under this new option. For the
beginning, check for it in the common code.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

arch/x86/kernel/cpu/hypervisor.c

@@ -28,8 +28,10 @@
 
 static const __initconst struct hypervisor_x86 * const hypervisors[] =
 {
-#ifdef CONFIG_XEN
+#ifdef CONFIG_XEN_PV
 	&x86_hyper_xen_pv,
+#endif
+#ifdef CONFIG_XEN_PVHVM
 	&x86_hyper_xen_hvm,
 #endif
 	&x86_hyper_vmware,

arch/x86/kernel/process_64.c

@@ -446,7 +446,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 		     task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
 		__switch_to_xtra(prev_p, next_p, tss);
 
-#ifdef CONFIG_XEN
+#ifdef CONFIG_XEN_PV
 	/*
 	 * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
 	 * current_pt_regs()->flags may not match the current task's

arch/x86/xen/Kconfig

@@ -6,7 +6,6 @@ config XEN
 	bool "Xen guest support"
 	depends on PARAVIRT
 	select PARAVIRT_CLOCK
-	select XEN_HAVE_PVMMU
 	select XEN_HAVE_VPMU
 	depends on X86_64 || (X86_32 && X86_PAE)
 	depends on X86_LOCAL_APIC && X86_TSC
@@ -15,18 +14,32 @@ config XEN
 	  kernel to boot in a paravirtualized environment under the
 	  Xen hypervisor.
 
+config XEN_PV
+	bool "Xen PV guest support"
+	default y
+	depends on XEN
+	select XEN_HAVE_PVMMU
+	help
+	  Support running as a Xen PV guest.
+
 config XEN_DOM0
-	def_bool y
-	depends on XEN && PCI_XEN && SWIOTLB_XEN
+	bool "Xen PV Dom0 support"
+	default y
+	depends on XEN_PV && PCI_XEN && SWIOTLB_XEN
 	depends on X86_IO_APIC && ACPI && PCI
+	help
+	  Support running as a Xen PV Dom0 guest.
 
 config XEN_PVHVM
-	def_bool y
+	bool "Xen PVHVM guest support"
+	default y
 	depends on XEN && PCI && X86_LOCAL_APIC
+	help
+	  Support running as a Xen PVHVM guest.
 
 config XEN_512GB
 	bool "Limit Xen pv-domain memory to 512GB"
-	depends on XEN && X86_64
+	depends on XEN_PV && X86_64
 	default y
 	help
 	  Limit paravirtualized user domains to 512GB of RAM.