[PATCH] Adds Kconfig option for Cross Memory Attach

[PATCH] Adds Kconfig option for Cross Memory Attach

[Christopher Yeoh]

Hi Andrew,

Attached is a patch which you asked for a while back which adds a
Kconfig option to allow people who don't want cross memory attach to not
have it included in their build.

Regards,

Chris
-- 
cyeoh@au.ibm.com

Signed-off-by: Chris Yeoh <yeohc@au1.ibm.com>
 Kconfig  |   11 +++++++++++
 Makefile |    7 +++++--
 2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index e338407..7619f90 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -379,3 +379,14 @@ config CLEANCACHE
 	  in a negligible performance hit.
 
 	  If unsure, say Y to enable cleancache
+
+config CROSS_MEMORY_ATTACH
+	bool "Cross Memory Support"
+	depends on MMU
+	default y
+	help
+	  Enabling this option adds the system calls process_vm_readv and
+	  process_vm_writev which allow a process with the correct privileges
+	  to directly read from or write to to another process's address space.
+	  See the man page for more details.
+
diff --git a/mm/Makefile b/mm/Makefile
index 50ec00e..1ddd00f 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -5,8 +5,11 @@
 mmu-y			:= nommu.o
 mmu-$(CONFIG_MMU)	:= fremap.o highmem.o madvise.o memory.o mincore.o \
 			   mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
-			   vmalloc.o pagewalk.o pgtable-generic.o \
-			   process_vm_access.o
+			   vmalloc.o pagewalk.o pgtable-generic.o
+
+ifdef CONFIG_CROSS_MEMORY_ATTACH
+mmu-$(CONFIG_MMU)	+= process_vm_access.o
+endif
 
 obj-y			:= filemap.o mempool.o oom_kill.o fadvise.o \
 			   maccess.o page_alloc.o page-writeback.o \

Re: [PATCH] Adds Kconfig option for Cross Memory Attach

[Randy Dunlap]

On 04/22/2012 09:12 PM, Christopher Yeoh wrote:

> Hi Andrew,
> 
> Attached is a patch which you asked for a while back which adds a
> Kconfig option to allow people who don't want cross memory attach to not
> have it included in their build.


and it shouldn't be default y.

Linus has written a diatribe on [not] making new options
default to y.

-- 
~Randy

Re: [PATCH] Adds Kconfig option for Cross Memory Attach

[Christopher Yeoh]

On Mon, 23 Apr 2012 08:48:52 -0700
Randy Dunlap <rdunlap@xenotime.net> wrote:
> On 04/22/2012 09:12 PM, Christopher Yeoh wrote:
> 
> > Hi Andrew,
> > 
> > Attached is a patch which you asked for a while back which adds a
> > Kconfig option to allow people who don't want cross memory attach
> > to not have it included in their build.
> 
> 
> and it shouldn't be default y.
> 
> Linus has written a diatribe on [not] making new options
> default to y.

I'm not that fussed, but currently CMA is enabled whether you like it
or not. This just allows you to disable it. IIRC there was an exception
where a new config option allows you to disable an old feature
(although CMA has not been out that long).

Regards,

Chris
-- 
cyeoh@au.ibm.com