[PATCH] Dynamic hugepage addresses for ppc64

Paulus, I think this is now a reasonable candidate for the post-2.6.13
queue.

Relax address restrictions for hugepages on ppc64

Presently, 64-bit applications on ppc64 may only use hugepages in the
address region from 1-1.5T.  Furthermore, if hugepages are enabled in
the kernel config, they may only use hugepages and never normal pages
in this area.  This patch relaxes this restriction, allowing any
address to be used with hugepages, but with a 1TB granularity.  That
is if you map a hugepage anywhere in the region 1TB-2TB, that entire
area will be reserved exclusively for hugepages for the remainder of
the process's lifetime.  This works analagously to hugepages in 32-bit
applications, where hugepages can be mapped anywhere, but with 256MB
(mmu segment) granularity.

This patch applies on top of the four level pagetable patch
(http://patchwork.ozlabs.org/linuxppc64/patch?id=1936).

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 12 insertions, 11 deletions

diff --git a/arch/ppc64/mm/slb_low.S b/arch/ppc64/mm/slb_low.S
index f20fc52483a7..bab255889c58 100644
--- a/arch/ppc64/mm/slb_low.S
+++ b/arch/ppc64/mm/slb_low.S
@@ -89,28 +89,29 @@ END_FTR_SECTION_IFSET(CPU_FTR_16M_PAGE)
         b       9f
 
 0:      /* user address: proto-VSID = context<<15 | ESID */
-        li      r11,SLB_VSID_USER
-
         srdi.   r9,r3,USER_ESID_BITS
         bne-    8f                      /* invalid ea bits set */
 
 #ifdef CONFIG_HUGETLB_PAGE
 BEGIN_FTR_SECTION
-        /* check against the hugepage ranges */
-        cmpldi  r3,(TASK_HPAGE_END>>SID_SHIFT)
-        bge     6f                      /* >= TASK_HPAGE_END */
-        cmpldi  r3,(TASK_HPAGE_BASE>>SID_SHIFT)
-        bge     5f                      /* TASK_HPAGE_BASE..TASK_HPAGE_END */
+        lhz     r9,PACAHIGHHTLBAREAS(r13)
+        srdi    r11,r3,(HTLB_AREA_SHIFT-SID_SHIFT)
+        srd     r9,r9,r11
+        andi.   r9,r9,1
+        bne     5f
+
+        li      r11,SLB_VSID_USER
+
         cmpldi  r3,16
-        bge     6f                      /* 4GB..TASK_HPAGE_BASE */
+        bge     6f
 
-        lhz     r9,PACAHTLBSEGS(r13)
+        lhz     r9,PACALOWHTLBAREAS(r13)
         srd     r9,r9,r3
         andi.   r9,r9,1
+
         beq     6f
 
-5:      /* this is a hugepage user address */
-        li      r11,(SLB_VSID_USER|SLB_VSID_L)
+5:      li      r11,SLB_VSID_USER|SLB_VSID_L
 END_FTR_SECTION_IFSET(CPU_FTR_16M_PAGE)
 #endif /* CONFIG_HUGETLB_PAGE */