From 58a84aa92723d1ac3e1cc4e3b0ff49291663f7e1 Mon Sep 17 00:00:00 2001 From: Youquan Song Date: Thu, 8 Dec 2011 14:34:18 -0800 Subject: thp: set compound tail page _count to zero Commit 70b50f94f1644 ("mm: thp: tail page refcounting fix") keeps all page_tail->_count zero at all times. But the current kernel does not set page_tail->_count to zero if a 1GB page is utilized. So when an IOMMU 1GB page is used by KVM, it wil result in a kernel oops because a tail page's _count does not equal zero. kernel BUG at include/linux/mm.h:386! invalid opcode: 0000 [#1] SMP Call Trace: gup_pud_range+0xb8/0x19d get_user_pages_fast+0xcb/0x192 ? trace_hardirqs_off+0xd/0xf hva_to_pfn+0x119/0x2f2 gfn_to_pfn_memslot+0x2c/0x2e kvm_iommu_map_pages+0xfd/0x1c1 kvm_iommu_map_memslots+0x7c/0xbd kvm_iommu_map_guest+0xaa/0xbf kvm_vm_ioctl_assigned_device+0x2ef/0xa47 kvm_vm_ioctl+0x36c/0x3a2 do_vfs_ioctl+0x49e/0x4e4 sys_ioctl+0x5a/0x7c system_call_fastpath+0x16/0x1b RIP gup_huge_pud+0xf2/0x159 Signed-off-by: Youquan Song Reviewed-by: Andrea Arcangeli Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9dd443d89d8..850009a7101 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -356,8 +356,8 @@ void prep_compound_page(struct page *page, unsigned long order) __SetPageHead(page); for (i = 1; i < nr_pages; i++) { struct page *p = page + i; - __SetPageTail(p); + set_page_count(p, 0); p->first_page = page; } } -- cgit v1.2.3-70-g09d2 From d021563888312018ca65681096f62e36c20e63cc Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 8 Dec 2011 14:34:27 -0800 Subject: mm: Ensure that pfn_valid() is called once per pageblock when reserving pageblocks setup_zone_migrate_reserve() expects that zone->start_pfn starts at pageblock_nr_pages aligned pfn otherwise we could access beyond an existing memblock resulting in the following panic if CONFIG_HOLES_IN_ZONE is not configured and we do not check pfn_valid: IP: [] setup_zone_migrate_reserve+0xcd/0x180 *pdpt = 0000000000000000 *pde = f000ff53f000ff53 Oops: 0000 [#1] SMP Pid: 1, comm: swapper Not tainted 3.0.7-0.7-pae #1 VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform EIP: 0060:[] EFLAGS: 00010006 CPU: 0 EIP is at setup_zone_migrate_reserve+0xcd/0x180 EAX: 000c0000 EBX: f5801fc0 ECX: 000c0000 EDX: 00000000 ESI: 000c01fe EDI: 000c01fe EBP: 00140000 ESP: f2475f58 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 Process swapper (pid: 1, ti=f2474000 task=f2472cd0 task.ti=f2474000) Call Trace: [] __setup_per_zone_wmarks+0xec/0x160 [] setup_per_zone_wmarks+0xf/0x20 [] init_per_zone_wmark_min+0x27/0x86 [] do_one_initcall+0x2b/0x160 [] kernel_init+0xbe/0x157 [] kernel_thread_helper+0x6/0xd Code: a5 39 f5 89 f7 0f 46 fd 39 cf 76 40 8b 03 f6 c4 08 74 32 eb 91 90 89 c8 c1 e8 0e 0f be 80 80 2f 86 c0 8b 14 85 60 2f 86 c0 89 c8 <2b> 82 b4 12 00 00 c1 e0 05 03 82 ac 12 00 00 8b 00 f6 c4 08 0f EIP: [] setup_zone_migrate_reserve+0xcd/0x180 SS:ESP 0068:f2475f58 CR2: 00000000000012b4 We crashed in pageblock_is_reserved() when accessing pfn 0xc0000 because highstart_pfn = 0x36ffe. The issue was introduced in 3.0-rc1 by 6d3163ce ("mm: check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE"). Make sure that start_pfn is always aligned to pageblock_nr_pages to ensure that pfn_valid s always called at the start of each pageblock. Architectures with holes in pageblocks will be correctly handled by pfn_valid_within in pageblock_is_reserved. Signed-off-by: Michal Hocko Signed-off-by: Mel Gorman Tested-by: Dang Bo Reviewed-by: KAMEZAWA Hiroyuki Cc: Andrea Arcangeli Cc: David Rientjes Cc: Arve Hjnnevg Cc: KOSAKI Motohiro Cc: John Stultz Cc: Dave Hansen Cc: [3.0+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 850009a7101..2b8ba3aebf6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3377,9 +3377,15 @@ static void setup_zone_migrate_reserve(struct zone *zone) unsigned long block_migratetype; int reserve; - /* Get the start pfn, end pfn and the number of blocks to reserve */ + /* + * Get the start pfn, end pfn and the number of blocks to reserve + * We have to be careful to be aligned to pageblock_nr_pages to + * make sure that we always check pfn_valid for the first page in + * the block. + */ start_pfn = zone->zone_start_pfn; end_pfn = start_pfn + zone->spanned_pages; + start_pfn = roundup(start_pfn, pageblock_nr_pages); reserve = roundup(min_wmark_pages(zone), pageblock_nr_pages) >> pageblock_order; -- cgit v1.2.3-70-g09d2