tmem: allow tmem to be disabled with Kconfig

Wrap the various tmem functions with the Kconfig generated CONFIG_TMEM
option allowing users to build Xen without tmem support.

Note that you have to use XEN_CONFIG_EXPERT to see this option.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/arch/x86/x86_64/compat/entry.S

@@ -345,6 +345,10 @@ compat_crash_page_fault:
 #define compat_kexec_op do_ni_hypercall
 #endif
 
+#ifndef CONFIG_TMEM
+#define do_tmem_op do_ni_hypercall
+#endif
+
 #ifndef CONFIG_XENOPROF
 #define compat_xenoprof_op do_ni_hypercall
 #endif

xen/arch/x86/x86_64/entry.S

@@ -681,6 +681,10 @@ ENTRY(exception_table)
 #define do_kexec_op do_ni_hypercall
 #endif
 
+#ifndef CONFIG_TMEM
+#define do_tmem_op do_ni_hypercall
+#endif
+
 #ifndef CONFIG_XENOPROF
 #define do_xenoprof_op do_ni_hypercall
 #endif

xen/common/Kconfig

@@ -87,6 +87,20 @@ config LATE_HWDOM
 
 	  If unsure, say N.
 
+# Enables transcendent memory support
+config TMEM
+	def_bool y
+	prompt "Transcendent Memory Support" if EXPERT = "y"
+	---help---
+	  Transcendent memory allows PV-aware guests to collaborate on memory
+	  usage. Guests can 'swap' their memory to the hypervisor or have an
+	  collective pool of memory shared across guests. The end result is
+	  less memory usage by guests allowing higher guest density.
+
+	  You also have to enable it on the Xen commandline by using tmem=1
+
+	  If unsure, say Y.
+
 # Adds support for Xenoprof
 config XENOPROF
 	def_bool y

xen/common/Makefile

@@ -49,8 +49,6 @@ obj-y += sysctl.o
 obj-y += tasklet.o
 obj-y += time.o
 obj-y += timer.o
-obj-y += tmem.o
-obj-y += tmem_xen.o
 obj-y += trace.o
 obj-y += version.o
 obj-y += vm_event.o
@@ -65,7 +63,11 @@ obj-bin-$(CONFIG_X86) += $(foreach n,decompress bunzip2 unxz unlzma unlzo unlz4
 obj-$(perfc)       += perfc.o
 obj-$(crash_debug) += gdbstub.o
 
-obj-$(CONFIG_COMPAT) += $(addprefix compat/,domain.o kernel.o memory.o multicall.o tmem_xen.o xlat.o)
+obj-$(CONFIG_COMPAT) += $(addprefix compat/,domain.o kernel.o memory.o multicall.o xlat.o)
+
+tmem-y := tmem.o tmem_xen.o
+tmem-$(CONFIG_COMPAT) += compat/tmem_xen.o
+obj-$(CONFIG_TMEM) += $(tmem-y)
 
 subdir-$(CONFIG_X86) += hvm
 

xen/include/xen/hypercall.h

@@ -133,9 +133,13 @@ extern long
 do_xsm_op(
     XEN_GUEST_HANDLE_PARAM(xsm_op_t) u_xsm_op);
 
+#ifdef CONFIG_TMEM
 extern long
 do_tmem_op(
     XEN_GUEST_HANDLE_PARAM(tmem_op_t) uops);
+#else
+#define do_tmem_op do_ni_hypercall
+#endif
 
 extern long
 do_xenoprof_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg);

xen/include/xen/tmem.h

@@ -11,9 +11,35 @@
 
 struct xen_sysctl_tmem_op;
 
+#ifdef CONFIG_TMEM
 extern int tmem_control(struct xen_sysctl_tmem_op *op);
 extern void tmem_destroy(void *);
 extern void *tmem_relinquish_pages(unsigned int, unsigned int);
 extern unsigned long tmem_freeable_pages(void);
+#else
+static inline int
+tmem_control(struct xen_sysctl_tmem_op *op)
+{
+    return -ENOSYS;
+}
+
+static inline void
+tmem_destroy(void *p)
+{
+    return;
+}
+
+static inline void *
+tmem_relinquish_pages(unsigned int x, unsigned int y)
+{
+    return NULL;
+}
+
+static inline unsigned long
+tmem_freeable_pages(void)
+{
+    return 0;
+}
+#endif /* CONFIG_TMEM */
 
 #endif /* __XEN_TMEM_H__ */

xen/include/xen/tmem_xen.h

@@ -63,6 +63,7 @@ static inline bool_t tmem_shared_auth(void)
     return opt_tmem_shared_auth;
 }
 
+#ifdef CONFIG_TMEM
 extern bool_t opt_tmem;
 static inline bool_t tmem_enabled(void)
 {
@@ -73,6 +74,16 @@ static inline void tmem_disable(void)
 {
     opt_tmem = 0;
 }
+#else
+static inline bool_t tmem_enabled(void)
+{
+    return 0;
+}
+
+static inline void tmem_disable(void)
+{
+}
+#endif /* CONFIG_TMEM */
 
 /*
  * Memory free page list management