From andrea@qumranet.com Tue Jan 22 12:09:04 2008 Date: Tue, 22 Jan 2008 21:08:58 +0100 From: Andrea Arcangeli To: Avi Kivity Cc: Izik Eidus , Andrew Morton , Nick Piggin , kvm-devel@lists.sourceforge.net, Benjamin Herrenschmidt , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com, holt@sgi.com, Hugh Dickins , clameter@sgi.com Subject: Re: [kvm-devel] [PATCH] mmu notifiers #v4 This last update avoids the need to refresh the young bit in the linux pte through follow_page and it allows tracking the accessed bits set by the hardware in the sptes without requiring vmexits in certain implementations. KVM side is here: http://marc.info/?l=kvm-devel&m=120103225508669&w=2 Signed-off-by: Andrea Arcangeli Index: linux-2.6/include/asm-generic/pgtable.h =================================================================== --- linux-2.6.orig/include/asm-generic/pgtable.h 2008-01-17 12:09:57.000000000 -0800 +++ linux-2.6/include/asm-generic/pgtable.h 2008-01-24 13:40:58.000000000 -0800 @@ -46,6 +46,7 @@ __young = ptep_test_and_clear_young(__vma, __address, __ptep); \ if (__young) \ flush_tlb_page(__vma, __address); \ + __young |= mmu_notifier_age_page((__vma)->vm_mm, __address); \ __young; \ }) #endif @@ -86,6 +87,7 @@ do { \ pte_t __pte; \ __pte = ptep_get_and_clear((__vma)->vm_mm, __address, __ptep); \ flush_tlb_page(__vma, __address); \ + mmu_notifier(invalidate_page, (__vma)->vm_mm, __address); \ __pte; \ }) #endif Index: linux-2.6/include/linux/mm_types.h =================================================================== --- linux-2.6.orig/include/linux/mm_types.h 2008-01-18 13:00:28.000000000 -0800 +++ linux-2.6/include/linux/mm_types.h 2008-01-24 13:40:58.000000000 -0800 @@ -10,6 +10,7 @@ #include #include #include +#include #include #include @@ -219,6 +220,10 @@ struct mm_struct { /* aio bits */ rwlock_t ioctx_list_lock; struct kioctx *ioctx_list; + +#ifdef CONFIG_MMU_NOTIFIER + struct mmu_notifier_head mmu_notifier; /* MMU notifier list */ +#endif }; #endif /* _LINUX_MM_TYPES_H */ Index: linux-2.6/include/linux/mmu_notifier.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6/include/linux/mmu_notifier.h 2008-01-24 13:40:58.000000000 -0800 @@ -0,0 +1,82 @@ +#ifndef _LINUX_MMU_NOTIFIER_H +#define _LINUX_MMU_NOTIFIER_H + +#include +#include + +#ifdef CONFIG_MMU_NOTIFIER + +struct mmu_notifier; + +struct mmu_notifier_ops { + void (*release)(struct mmu_notifier *mn, + struct mm_struct *mm); + int (*age_page)(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long address); + void (*invalidate_page)(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long address); + void (*invalidate_range)(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, unsigned long end); +}; + +struct mmu_notifier_head { + struct hlist_head head; + rwlock_t lock; +}; + +struct mmu_notifier { + struct hlist_node hlist; + const struct mmu_notifier_ops *ops; +}; + +#include + +extern void mmu_notifier_register(struct mmu_notifier *mn, + struct mm_struct *mm); +extern void mmu_notifier_unregister(struct mmu_notifier *mn, + struct mm_struct *mm); +extern void mmu_notifier_release(struct mm_struct *mm); +extern int mmu_notifier_age_page(struct mm_struct *mm, + unsigned long address); + +static inline void mmu_notifier_head_init(struct mmu_notifier_head *mnh) +{ + INIT_HLIST_HEAD(&mnh->head); + rwlock_init(&mnh->lock); +} + +#define mmu_notifier(function, mm, args...) \ + do { \ + struct mmu_notifier *__mn; \ + struct hlist_node *__n; \ + \ + if (unlikely(!hlist_empty(&(mm)->mmu_notifier.head))) { \ + read_lock(&(mm)->mmu_notifier.lock); \ + hlist_for_each_entry(__mn, __n, \ + &(mm)->mmu_notifier.head, \ + hlist) \ + if (__mn->ops->function) \ + __mn->ops->function(__mn, \ + mm, \ + args); \ + read_unlock(&(mm)->mmu_notifier.lock); \ + } \ + } while (0) + +#else /* CONFIG_MMU_NOTIFIER */ + +#define mmu_notifier_register(mn, mm) do {} while(0) +#define mmu_notifier_unregister(mn, mm) do {} while (0) +#define mmu_notifier_release(mm) do {} while (0) +#define mmu_notifier_age_page(mm, address) ({ 0; }) +#define mmu_notifier_head_init(mmh) do {} while (0) + +#define mmu_notifier(function, mm, args...) \ + do { } while (0) + +#endif /* CONFIG_MMU_NOTIFIER */ + +#endif /* _LINUX_MMU_NOTIFIER_H */ Index: linux-2.6/kernel/fork.c =================================================================== --- linux-2.6.orig/kernel/fork.c 2007-12-20 14:58:40.000000000 -0800 +++ linux-2.6/kernel/fork.c 2008-01-24 13:40:58.000000000 -0800 @@ -359,6 +359,7 @@ static struct mm_struct * mm_init(struct if (likely(!mm_alloc_pgd(mm))) { mm->def_flags = 0; + mmu_notifier_head_init(&mm->mmu_notifier); return mm; } free_mm(mm); Index: linux-2.6/mm/Kconfig =================================================================== --- linux-2.6.orig/mm/Kconfig 2008-01-23 19:23:31.000000000 -0800 +++ linux-2.6/mm/Kconfig 2008-01-24 13:40:58.000000000 -0800 @@ -193,3 +193,7 @@ config NR_QUICK config VIRT_TO_BUS def_bool y depends on !ARCH_NO_VIRT_TO_BUS + +config MMU_NOTIFIER + def_bool y + bool "MMU notifier, for paging KVM/RDMA" Index: linux-2.6/mm/Makefile =================================================================== --- linux-2.6.orig/mm/Makefile 2008-01-23 19:23:31.000000000 -0800 +++ linux-2.6/mm/Makefile 2008-01-24 13:40:58.000000000 -0800 @@ -30,4 +30,5 @@ obj-$(CONFIG_FS_XIP) += filemap_xip.o obj-$(CONFIG_MIGRATION) += migrate.o obj-$(CONFIG_SMP) += allocpercpu.o obj-$(CONFIG_QUICKLIST) += quicklist.o +obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o Index: linux-2.6/mm/hugetlb.c =================================================================== --- linux-2.6.orig/mm/hugetlb.c 2008-01-24 13:28:46.000000000 -0800 +++ linux-2.6/mm/hugetlb.c 2008-01-24 13:40:58.000000000 -0800 @@ -763,6 +763,7 @@ void __unmap_hugepage_range(struct vm_ar } spin_unlock(&mm->page_table_lock); flush_tlb_range(vma, start, end); + mmu_notifier(invalidate_range, mm, start, end); list_for_each_entry_safe(page, tmp, &page_list, lru) { list_del(&page->lru); put_page(page); Index: linux-2.6/mm/memory.c =================================================================== --- linux-2.6.orig/mm/memory.c 2008-01-23 19:15:39.000000000 -0800 +++ linux-2.6/mm/memory.c 2008-01-24 13:40:58.000000000 -0800 @@ -891,6 +891,7 @@ unsigned long zap_page_range(struct vm_a end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details); if (tlb) tlb_finish_mmu(tlb, address, end); + mmu_notifier(invalidate_range, mm, address, end); return end; } @@ -1319,7 +1320,7 @@ int remap_pfn_range(struct vm_area_struc { pgd_t *pgd; unsigned long next; - unsigned long end = addr + PAGE_ALIGN(size); + unsigned long start = addr, end = addr + PAGE_ALIGN(size); struct mm_struct *mm = vma->vm_mm; int err; @@ -1360,6 +1361,7 @@ int remap_pfn_range(struct vm_area_struc if (err) break; } while (pgd++, addr = next, addr != end); + mmu_notifier(invalidate_range, mm, start, end); return err; } EXPORT_SYMBOL(remap_pfn_range); @@ -1443,7 +1445,7 @@ int apply_to_page_range(struct mm_struct { pgd_t *pgd; unsigned long next; - unsigned long end = addr + size; + unsigned long start = addr, end = addr + size; int err; BUG_ON(addr >= end); @@ -1454,6 +1456,7 @@ int apply_to_page_range(struct mm_struct if (err) break; } while (pgd++, addr = next, addr != end); + mmu_notifier(invalidate_range, mm, start, end); return err; } EXPORT_SYMBOL_GPL(apply_to_page_range); Index: linux-2.6/mm/mmap.c =================================================================== --- linux-2.6.orig/mm/mmap.c 2008-01-18 20:30:47.000000000 -0800 +++ linux-2.6/mm/mmap.c 2008-01-24 13:40:58.000000000 -0800 @@ -1747,6 +1747,7 @@ static void unmap_region(struct mm_struc free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS, next? next->vm_start: 0); tlb_finish_mmu(tlb, start, end); + mmu_notifier(invalidate_range, mm, start, end); } /* @@ -2043,6 +2044,7 @@ void exit_mmap(struct mm_struct *mm) vm_unacct_memory(nr_accounted); free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0); tlb_finish_mmu(tlb, 0, end); + mmu_notifier_release(mm); /* * Walk the list again, actually closing and freeing it, Index: linux-2.6/mm/mmu_notifier.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6/mm/mmu_notifier.c 2008-01-24 13:40:58.000000000 -0800 @@ -0,0 +1,68 @@ +/* + * linux/mm/mmu_notifier.c + * + * Copyright (C) 2008 Qumranet, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#include +#include + +void mmu_notifier_release(struct mm_struct *mm) +{ + struct mmu_notifier *mn; + struct hlist_node *n, *tmp; + + if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) { + read_lock(&mm->mmu_notifier.lock); + hlist_for_each_entry_safe(mn, n, tmp, + &mm->mmu_notifier.head, hlist) { + if (mn->ops->release) + mn->ops->release(mn, mm); + hlist_del(&mn->hlist); + } + read_unlock(&mm->mmu_notifier.lock); + } +} + +/* + * If no young bitflag is supported by the hardware, ->age_page can + * unmap the address and return 1 or 0 depending if the mapping previously + * existed or not. + */ +int mmu_notifier_age_page(struct mm_struct *mm, unsigned long address) +{ + struct mmu_notifier *mn; + struct hlist_node *n, *tmp; + int young = 0; + + if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) { + read_lock(&mm->mmu_notifier.lock); + hlist_for_each_entry_safe(mn, n, tmp, + &mm->mmu_notifier.head, hlist) { + if (mn->ops->age_page) + young |= mn->ops->age_page(mn, mm, address); + } + read_unlock(&mm->mmu_notifier.lock); + } + + return young; +} + +void mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) +{ + write_lock(&mm->mmu_notifier.lock); + hlist_add_head(&mn->hlist, &mm->mmu_notifier.head); + write_unlock(&mm->mmu_notifier.lock); +} +EXPORT_SYMBOL_GPL(mmu_notifier_register); + +void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm) +{ + write_lock(&mm->mmu_notifier.lock); + hlist_del(&mn->hlist); + write_unlock(&mm->mmu_notifier.lock); +} +EXPORT_SYMBOL_GPL(mmu_notifier_unregister);