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authorDavid Gibson <david@gibson.dropbear.id.au>2005-11-07 03:57:52 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-07 10:53:23 -0500
commit7d24f0b8a53261709938ffabe3e00f88f6498df9 (patch)
tree95e192cdda64cbb7bb64451442c93a64d3932757 /arch/powerpc/mm/hugetlbpage.c
parent0b154bb7d0cce80e9c0bcf11d4f9e71b59409d26 (diff)
[PATCH] ppc64: Fix bug in SLB miss handler for hugepages
This patch, however, should be applied on top of the 64k-page-size patch to fix some problems with hugepage (some pre-existing, another introduced by this patch). The patch fixes a bug in the SLB miss handler for hugepages on ppc64 introduced by the dynamic hugepage patch (commit id c594adad5653491813959277fb87a2fef54c4e05) due to a misunderstanding of the srd instruction's behaviour (mea culpa). The problem arises when a 64-bit process maps some hugepages in the low 4GB of the address space (unusual). In this case, as well as the 256M segment in question being marked for hugepages, other segments at 32G intervals will be incorrectly marked for hugepages. In the process, this patch tweaks the semantics of the hugepage bitmaps to be more sensible. Previously, an address below 4G was marked for hugepages if the appropriate segment bit in the "low areas" bitmask was set *or* if the low bit in the "high areas" bitmap was set (which would mark all addresses below 1TB for hugepage). With this patch, any given address is governed by a single bitmap. Addresses below 4GB are marked for hugepage if and only if their bit is set in the "low areas" bitmap (256M granularity). Addresses between 4GB and 1TB are marked for hugepage iff the low bit in the "high areas" bitmap is set. Higher addresses are marked for hugepage iff their bit in the "high areas" bitmap is set (1TB granularity). To avoid conflicts, this patch must be applied on top of BenH's pending patch for 64k base page size [0]. As such, this patch also addresses a hugepage problem introduced by that patch. That patch allows hugepages of 1MB in size on hardware which supports it, however, that won't work when using 4k pages (4 level pagetable), because in that case hugepage PTEs are stored at the PMD level, and each PMD entry maps 2MB. This patch simply disallows hugepages in that case (we can do something cleverer to re-enable them some other day). Built, booted, and a handful of hugepage related tests passed on POWER5 LPAR (both ARCH=powerpc and ARCH=ppc64). [0] http://gate.crashing.org/~benh/ppc64-64k-pages.diff Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/powerpc/mm/hugetlbpage.c')
-rw-r--r--arch/powerpc/mm/hugetlbpage.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 0073a04047e4..426c269e552e 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -212,6 +212,12 @@ static int prepare_high_area_for_htlb(struct mm_struct *mm, unsigned long area)
212 212
213 BUG_ON(area >= NUM_HIGH_AREAS); 213 BUG_ON(area >= NUM_HIGH_AREAS);
214 214
215 /* Hack, so that each addresses is controlled by exactly one
216 * of the high or low area bitmaps, the first high area starts
217 * at 4GB, not 0 */
218 if (start == 0)
219 start = 0x100000000UL;
220
215 /* Check no VMAs are in the region */ 221 /* Check no VMAs are in the region */
216 vma = find_vma(mm, start); 222 vma = find_vma(mm, start);
217 if (vma && (vma->vm_start < end)) 223 if (vma && (vma->vm_start < end))