From: Scott Moser <smoser@redhat.com>
Subject: [PATCH RHEL5u1] bz285981 Softlockups when using Cell apps with 	hugetlbfs
Date: Tue, 11 Sep 2007 10:56:15 -0400 (EDT)
Bugzilla: 285981
Message-Id: <Pine.LNX.4.64.0709111055340.27130@squad5-lp1.lab.boston.redhat.com>
Changelog: [ppc64] Fix SPU slb size and invalidation on hugepage faults


RHBZ#: 285981
------
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=285981

Description:
------------
Fix SPU slb size and invalidation on hugepage faults

Looks like the spu data segment handler has an artifact of the
address-space slices work - hugepage sizes aren't being encoded
correctly in the SLBs inserted. This results in an infinite loop
of hash misses when the SPE touches a hugepage mapping.

This change corrects the page size encoding, and fixes the SPE/SPU
typo in the SLB invalidation paths, so that the invalidation
actually occurs.

No applications that use Cell SPEs AND hugetlbfs will work without this
patch.  Attempting to access hugepages from a SPE will result in 100% CPU
load.

This bug is reproducible with IBM's "CellBladeTester" application, and
additionally with two demo apps from the Cell SDK, "fft" and "julia_set".
The SDK is available at [1]

RHEL Version Found:
-------------------
2.6.18-39.el5

Test Status:
------------
To ensure cross platform build, this patch has been built with brew
applied to kernel-2.6.18-46.el5. The build is available at [2].

This patch has been tested by Jeremy Kerr of IBM.

Proposed Patch:
----------------
Please review and ACK for RHEL5.1

--
 arch/powerpc/mm/hash_utils_64.c        |    8 ++++----
 arch/powerpc/mm/hugetlbpage.c          |    4 ++--
 arch/powerpc/platforms/cell/spu_base.c |    6 +++---
 3 files changed, 9 insertions(+), 9 deletions(-)
Index: b/arch/powerpc/mm/hash_utils_64.c
===================================================================
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -587,7 +587,7 @@ void demote_segment_4k(struct mm_struct 
 	mm->context.sllp = SLB_VSID_USER | mmu_psize_defs[MMU_PAGE_4K].sllp;
 	get_paca()->context = mm->context;
 	slb_flush_and_rebolt();
-#ifdef CONFIG_SPE_BASE
+#ifdef CONFIG_SPU_BASE
 	spu_flush_all_slbs(mm);
 #endif
 #endif
@@ -711,7 +711,7 @@ int hash_page(unsigned long ea, unsigned
 				       "non-cacheable mapping\n");
 				psize = mmu_vmalloc_psize = MMU_PAGE_4K;
 			}
-#ifdef CONFIG_SPE_BASE
+#ifdef CONFIG_SPU_BASE
 			spu_flush_all_slbs(mm);
 #endif
 		}
@@ -719,7 +719,7 @@ int hash_page(unsigned long ea, unsigned
 			if (psize != get_paca()->context.user_psize) {
 				get_paca()->context = mm->context;
 				slb_flush_and_rebolt();
-#ifdef CONFIG_SPE_BASE
+#ifdef CONFIG_SPU_BASE
 				spu_flush_all_slbs(mm);
 #endif
 			}
@@ -728,7 +728,7 @@ int hash_page(unsigned long ea, unsigned
 			get_paca()->vmalloc_sllp =
 				mmu_psize_defs[mmu_vmalloc_psize].sllp;
 			slb_flush_and_rebolt();
-#ifdef CONFIG_SPE_BASE
+#ifdef CONFIG_SPU_BASE
 			spu_flush_all_slbs(mm);
 #endif
 		}
Index: b/arch/powerpc/mm/hugetlbpage.c
===================================================================
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -513,8 +513,8 @@ int prepare_hugepage_range(unsigned long
 	if ((addr + len) > 0x100000000UL)
 		err = open_high_hpage_areas(current->mm,
 					    HTLB_AREA_MASK(addr, len));
-#ifdef CONFIG_SPE_BASE
-	spu_flush_all_slbs(mm);
+#ifdef CONFIG_SPU_BASE
+	spu_flush_all_slbs(current->mm);
 #endif
 	if (err) {
 		printk(KERN_DEBUG "prepare_hugepage_range(%lx, %lx)"
Index: b/arch/powerpc/platforms/cell/spu_base.c
===================================================================
--- a/arch/powerpc/platforms/cell/spu_base.c
+++ b/arch/powerpc/platforms/cell/spu_base.c
@@ -147,10 +147,10 @@ static int __spu_trap_data_seg(struct sp
 
 	switch(REGION_ID(ea)) {
 	case USER_REGION_ID:
-#ifdef CONFIG_PPC_MM_SLICES
-		psize = get_slice_psize(mm, ea);
-#else
 		psize = mm->context.user_psize;
+#ifdef CONFIG_HUGETLB_PAGE
+		if (in_hugepage_area(mm->context, ea))
+			psize = mmu_huge_psize;
 #endif
 		vsid = (get_vsid(mm->context.id, ea) << SLB_VSID_SHIFT) |
 				SLB_VSID_USER;