Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750886AbVKCF0s (ORCPT ); Thu, 3 Nov 2005 00:26:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750881AbVKCF0s (ORCPT ); Thu, 3 Nov 2005 00:26:48 -0500 Received: from ozlabs.org ([203.10.76.45]:26055 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S1750758AbVKCF0r (ORCPT ); Thu, 3 Nov 2005 00:26:47 -0500 Date: Thu, 3 Nov 2005 16:26:34 +1100 From: David Gibson To: Paul Mackerras Cc: Benjamin Herrenschmidt , Andrew Morton , linuxppc64-dev , Linus Torvalds , Linux Kernel list Subject: ppc64: Fix bug in SLB miss handler for hugepages Message-ID: <20051103052634.GD24772@localhost.localdomain> Mail-Followup-To: Paul Mackerras , Benjamin Herrenschmidt , Andrew Morton , linuxppc64-dev , Linus Torvalds , Linux Kernel list References: <1130915220.20136.14.camel@gaston> <1130916198.20136.17.camel@gaston> <17257.33037.210237.986072@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17257.33037.210237.986072@cargo.ozlabs.ibm.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7043 Lines: 164 On Thu, Nov 03, 2005 at 02:16:29PM +1100, Paul Mackerras wrote: > Benjamin Herrenschmidt writes: > > > It took a while, but finally, here is the 64K pages support patch for > > ppc64. This patch adds a new CONFIG_PPC_64K_PAGES which, when enabled, > > changes the kernel base page size to 64K. The resulting kernel still > > boots on any hardware. On current machines with 4K pages support only, > > the kernel will maintain 16 "subpages" for each 64K page > > transparently. > > > > Note that while real 64K capable HW has been tested, the current patch > > will not enable it yet as such hardware is not released yet, and I'm > > still verifying with the firmware architects the proper to get the > > information from the newer hypervisors. > > > > Signed-off-by: Benjamin Herrenschmidt > > Acked-by: Paul Mackerras This patch, however, should be applied on top 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 Index: working-2.6/arch/powerpc/mm/slb_low.S =================================================================== --- working-2.6.orig/arch/powerpc/mm/slb_low.S 2005-11-03 14:52:16.000000000 +1100 +++ working-2.6/arch/powerpc/mm/slb_low.S 2005-11-03 14:55:56.000000000 +1100 @@ -80,12 +80,17 @@ BEGIN_FTR_SECTION b 1f END_FTR_SECTION_IFCLR(CPU_FTR_16M_PAGE) + cmpldi r10,16 + + lhz r9,PACALOWHTLBAREAS(r13) + mr r11,r10 + blt 5f + lhz r9,PACAHIGHHTLBAREAS(r13) srdi r11,r10,(HTLB_AREA_SHIFT-SID_SHIFT) - srd r9,r9,r11 - lhz r11,PACALOWHTLBAREAS(r13) - srd r11,r11,r10 - or. r9,r9,r11 + +5: srd r9,r9,r11 + andi. r9,r9,1 beq 1f _GLOBAL(slb_miss_user_load_huge) li r11,0 Index: working-2.6/arch/powerpc/mm/hash_utils_64.c =================================================================== --- working-2.6.orig/arch/powerpc/mm/hash_utils_64.c 2005-11-03 14:52:16.000000000 +1100 +++ working-2.6/arch/powerpc/mm/hash_utils_64.c 2005-11-03 15:40:56.000000000 +1100 @@ -329,12 +329,14 @@ */ if (mmu_psize_defs[MMU_PAGE_16M].shift) mmu_huge_psize = MMU_PAGE_16M; + /* With 4k/4level pagetables, we can't (for now) cope with a + * huge page size < PMD_SIZE */ else if (mmu_psize_defs[MMU_PAGE_1M].shift) mmu_huge_psize = MMU_PAGE_1M; /* Calculate HPAGE_SHIFT and sanity check it */ - if (mmu_psize_defs[mmu_huge_psize].shift > 16 && - mmu_psize_defs[mmu_huge_psize].shift < 28) + if (mmu_psize_defs[mmu_huge_psize].shift > MIN_HUGEPTE_SHIFT && + mmu_psize_defs[mmu_huge_psize].shift < SID_SHIFT) HPAGE_SHIFT = mmu_psize_defs[mmu_huge_psize].shift; else HPAGE_SHIFT = 0; /* No huge pages dude ! */ Index: working-2.6/include/asm-ppc64/pgtable-4k.h =================================================================== --- working-2.6.orig/include/asm-ppc64/pgtable-4k.h 2005-11-03 14:52:16.000000000 +1100 +++ working-2.6/include/asm-ppc64/pgtable-4k.h 2005-11-03 15:38:40.000000000 +1100 @@ -23,6 +23,9 @@ #define PMD_SIZE (1UL << PMD_SHIFT) #define PMD_MASK (~(PMD_SIZE-1)) +/* With 4k base page size, hugepage PTEs go at the PMD level */ +#define MIN_HUGEPTE_SHIFT PMD_SHIFT + /* PUD_SHIFT determines what a third-level page table entry can map */ #define PUD_SHIFT (PMD_SHIFT + PMD_INDEX_SIZE) #define PUD_SIZE (1UL << PUD_SHIFT) Index: working-2.6/include/asm-ppc64/pgtable-64k.h =================================================================== --- working-2.6.orig/include/asm-ppc64/pgtable-64k.h 2005-11-03 14:52:16.000000000 +1100 +++ working-2.6/include/asm-ppc64/pgtable-64k.h 2005-11-03 15:39:07.000000000 +1100 @@ -14,6 +14,9 @@ #define PTRS_PER_PMD (1 << PMD_INDEX_SIZE) #define PTRS_PER_PGD (1 << PGD_INDEX_SIZE) +/* With 4k base page size, hugepage PTEs go at the PMD level */ +#define MIN_HUGEPTE_SHIFT PAGE_SHIFT + /* PMD_SHIFT determines what a second-level page table entry can map */ #define PMD_SHIFT (PAGE_SHIFT + PTE_INDEX_SIZE) #define PMD_SIZE (1UL << PMD_SHIFT) Index: working-2.6/arch/powerpc/mm/hugetlbpage.c =================================================================== --- working-2.6.orig/arch/powerpc/mm/hugetlbpage.c 2005-11-03 14:52:16.000000000 +1100 +++ working-2.6/arch/powerpc/mm/hugetlbpage.c 2005-11-03 15:56:34.000000000 +1100 @@ -212,6 +212,12 @@ BUG_ON(area >= NUM_HIGH_AREAS); + /* Hack, so that each addresses is controlled by exactly one + * of the high or low area bitmaps, the first high area starts + * at 4GB, not 0 */ + if (start == 0) + start = 0x100000000UL; + /* Check no VMAs are in the region */ vma = find_vma(mm, start); if (vma && (vma->vm_start < end)) -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/people/dgibson - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/