[PATCH] spufs: always map local store non-guarded

When fixing spufs to map the 'mem' file backing store cacheable,
I incorrectly set the physical mapping to use both cache-inhibited
and guarded mapping, which resulted in a serious performance
degradation.

Accessing the real local store memory needs to be cache-inhibited,
in order to maintain data consistency, but since it is actual
RAM, there is no point in a guarded mapping.

Debugged-by: Michael Ellerman [off-list ref]
Signed-off-by: Arnd Bergmann <redacted>
---

This fixes a regression in 2.6.19, please merge.

Index: linux-2.6/arch/powerpc/platforms/cell/spufs/file.c
===================================================================

--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/file.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/file.c

@@ -104,11 +104,11 @@ spufs_mem_mmap_nopage(struct vm_area_str
 
 	if (ctx->state == SPU_STATE_SAVED) {
 		vma->vm_page_prot = __pgprot(pgprot_val(vma->vm_page_prot)
-					& ~(_PAGE_NO_CACHE | _PAGE_GUARDED));
+							& ~_PAGE_NO_CACHE);
 		page = vmalloc_to_page(ctx->csa.lscsa->ls + offset);
 	} else {
 		vma->vm_page_prot = __pgprot(pgprot_val(vma->vm_page_prot)
-					| _PAGE_NO_CACHE | _PAGE_GUARDED);
+							| _PAGE_NO_CACHE);
 		page = pfn_to_page((ctx->spu->local_store_phys + offset)
 				   >> PAGE_SHIFT);
 	}

On Thu, 2006-11-02 at 13:46 +0100, Arnd Bergmann wrote:

When fixing spufs to map the 'mem' file backing store cacheable,
I incorrectly set the physical mapping to use both cache-inhibited
and guarded mapping, which resulted in a serious performance
degradation.

Accessing the real local store memory needs to be cache-inhibited,
in order to maintain data consistency, but since it is actual
RAM, there is no point in a guarded mapping.

Debugged-by: Michael Ellerman [off-list ref]
Signed-off-by: Arnd Bergmann <redacted>
---

Looks good, cheers

Acked-by: Michael Ellerman <redacted>

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person