tmem: default to off

As a short term alternative to deleting the code, default its building
to off (overridable in EXPERT mode only). Additionally make sure other
related baggage (LZO code) won't be carried when the option is off (with
TMEM scheduled to be deleted anyway, I didn't want to introduce a
separate Kconfig option to control the LZO compression code, and hence
CONFIG_TMEM is used directly there). Similarly I couldn't be bothered to
add actual content to the command line option doc for the two affected
options.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Release-acked-by: Juergen Gross <jgross@suse.com>

docs/misc/xen-command-line.pandoc

@@ -1969,9 +1969,15 @@ pages) must also be specified via the tbuf_size parameter.
 ### tmem
 > `= <boolean>`
 
+This option (and its underlying code) is going to go away in a future
+Xen version.
+
 ### tmem_compress
 > `= <boolean>`
 
+This option (and its underlying code) is going to go away in a future
+Xen version.
+
 ### tsc (x86)
 > `= unstable | skewed | stable:socket`
 

xen/common/Kconfig

@@ -78,17 +78,19 @@ config KEXEC
 	  If unsure, say Y.
 
 config TMEM
-	def_bool y
-	prompt "Transcendent Memory Support" if EXPERT = "y"
+	bool "Transcendent Memory Support (deprecated)" 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
+	  You also have to enable it on the Xen commandline by using tmem=1.
 
-	  If unsure, say Y.
+	  WARNING: This option (and its underlying code) is going to go away
+	  in a future Xen version.
+
+	  If unsure, say N.
 
 config XENOPROF
 	def_bool y

xen/common/Makefile

@@ -21,7 +21,7 @@ obj-$(CONFIG_KEXEC) += kimage.o
 obj-y += lib.o
 obj-$(CONFIG_NEEDS_LIST_SORT) += list_sort.o
 obj-$(CONFIG_LIVEPATCH) += livepatch.o livepatch_elf.o
-obj-y += lzo.o
+obj-$(CONFIG_TMEM) += lzo.o
 obj-$(CONFIG_MEM_ACCESS) += mem_access.o
 obj-y += memory.o
 obj-y += monitor.o
@@ -66,8 +66,9 @@ obj-bin-y += warning.init.o
 obj-$(CONFIG_XENOPROF) += xenoprof.o
 obj-y += xmalloc_tlsf.o
 
-obj-bin-$(CONFIG_X86) += $(foreach n,decompress bunzip2 unxz unlzma unlzo unlz4 earlycpio,$(n).init.o)
-
+lzo-y := lzo
+lzo-$(CONFIG_TMEM) :=
+obj-bin-$(CONFIG_X86) += $(foreach n,decompress bunzip2 unxz unlzma $(lzo-y) unlzo unlz4 earlycpio,$(n).init.o)
 
 obj-$(CONFIG_COMPAT) += $(addprefix compat/,domain.o kernel.o memory.o multicall.o xlat.o)
 

xen/common/lzo.c

@@ -105,6 +105,8 @@
 #define get_unaligned_le16(_p) (*(u16 *)(_p))
 #define get_unaligned_le32(_p) (*(u32 *)(_p))
 
+#ifdef CONFIG_TMEM
+
 static noinline size_t
 lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
                     unsigned char *out, size_t *out_len,
@@ -362,6 +364,11 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
     return LZO_E_OK;
 }
 
+# define INIT
+#else /* CONFIG_TMEM */
+# include "decompress.h"
+#endif /* CONFIG_TMEM */
+
 /*
  *  LZO1X Decompressor from LZO
  *
@@ -391,8 +398,8 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
  */
 #define MAX_255_COUNT      ((((size_t)~0) / 255) - 2)
 
-int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
-                          unsigned char *out, size_t *out_len)
+int INIT lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
+                               unsigned char *out, size_t *out_len)
 {
     unsigned char *op;
     const unsigned char *ip;