[POWERPC] Spufs support for 64K LS mappings on 4K kernels

This adds an option to spufs when the kernel is configured for
4K page to give it the ability to use 64K pages for SPE local store
mappings.

Currently, we are optimistic and try order 4 allocations when creating
contexts. If that fails, the code will fallback to 4K automatically.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/cell/Kconfig

@@ -35,6 +35,21 @@ config SPU_FS
 	  Units on machines implementing the Broadband Processor
 	  Architecture.
 
+config SPU_FS_64K_LS
+	bool "Use 64K pages to map SPE local  store"
+	# we depend on PPC_MM_SLICES for now rather than selecting
+	# it because we depend on hugetlbfs hooks being present. We
+	# will fix that when the generic code has been improved to
+	# not require hijacking hugetlbfs hooks.
+	depends on SPU_FS && PPC_MM_SLICES && !PPC_64K_PAGES
+	default y
+	select PPC_HAS_HASH_64K
+	help
+	  This option causes SPE local stores to be mapped in process
+	  address spaces using 64K pages while the rest of the kernel
+	  uses 4K pages. This can improve performances of applications
+	  using multiple SPEs by lowering the TLB pressure on them.
+
 config SPU_BASE
 	bool
 	default n