[PATCH] uml: deprecate CONFIG_MODE_TT

Deprecate TT mode in Kconfig so that users won't select it, update the
MODE_SKAS description (it was largely obsolete and misleadin) and btw describe
advantages for high memory usage with CONFIG_STATIC_LINK.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 15 insertions, 7 deletions

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 450547a4b3be..78fb619bdb73 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -50,13 +50,15 @@ config IRQ_RELEASE_METHOD
 menu "UML-specific options"
 
 config MODE_TT
-        bool "Tracing thread support"
+        bool "Tracing thread support (DEPRECATED)"
         default n
         help
         This option controls whether tracing thread support is compiled
-        into UML.  This option is largely obsolete, given that skas0 provides
+        into UML. This option is largely obsolete, given that skas0 provides
         skas security and performance without needing to patch the host.
-        It is safe to say 'N' here.
+        It is safe to say 'N' here; saying 'Y' may cause additional problems
+        with the resulting binary even if you run UML in SKAS mode, and running
+        in TT mode is strongly *NOT RECOMMENDED*.
 
 config STATIC_LINK
         bool "Force a static link"
@@ -69,6 +71,9 @@ config STATIC_LINK
         for use in a chroot jail.  So, if you intend to run UML inside a
         chroot, and you disable CONFIG_MODE_TT, you probably want to say Y
         here.
+        Additionally, this option enables using higher memory spaces (up to
+        2.75G) for UML - disabling CONFIG_MODE_TT and enabling this option leads
+        to best results for this.
 
 config KERNEL_HALF_GIGS
         int "Kernel address space size (in .5G units)"
@@ -85,10 +90,13 @@ config MODE_SKAS
         default y
         help
         This option controls whether skas (separate kernel address space)
-        support is compiled in.  If you have applied the skas patch to the
-        host, then you certainly want to say Y here (and consider saying N
-        to CONFIG_MODE_TT).  Otherwise, it is safe to say Y.  Disabling this
-        option will shrink the UML binary slightly.
+        support is compiled in.
+        Unless you have specific needs to use TT mode (which applies almost only
+        to developers), you should say Y here.
+        SKAS mode will make use of the SKAS3 patch if it is applied on the host
+        (and your UML will run in SKAS3 mode), but if no SKAS patch is applied
+        on the host it will run in SKAS0 mode, which is anyway faster than TT
+        mode.
 
 source "arch/um/Kconfig.arch"
 source "mm/Kconfig"