From 6490a8dadf2f52197fb36f747fb710bb3d344908 Mon Sep 17 00:00:00 2001 From: Youquan Song Date: Fri, 2 Dec 2011 14:06:49 +1100 Subject: [PATCH] thp: add compound tail page _mapcount when mapped With the 3.2-rc kernel, the IOMMU 2M page in KVM works. While I try to us IOMMU 1GB page in KVM, I encounter a oops and 1GB page total fail to be used. The root cause is that 1GB page allocation calls gup_huge_pud() while 2M page calls gup_huge_pmd. If compound pages are used and the page is tail page, gup_huge_pmd increase _mapcount to record tail page are mapped while gup_huge_pud does not include this process. So when the mapped page is relesed, it will result in kernel oops because the page does not mark mapped. This patch add tail process for compound page in 1GB huge page which keeps the same process as 2M page. Reproduce like: 1. Add grub boot option: hugepagesz=1G hugepages=8 2. mount -t hugetlbfs -o pagesize=1G hugetlbfs /dev/hugepages 3.qemu-kvm -m 2048 -hda os-kvm.img -cpu kvm64 -smp 4 -mem-path /dev/hugepages -net none -device pci-assign,host=07:00.1 kernel BUG at mm/swap.c:114! invalid opcode: 0000 [#1] SMP Call Trace: [] put_page+0x15/0x37 [] kvm_release_pfn_clean+0x31/0x36 [] kvm_iommu_put_pages+0x94/0xb1 [] kvm_iommu_unmap_memslots+0x80/0xb6 [] ? kvm_iommu_put_pages+0xb1/0xb1 [] ? intel_iommu_attach_device+0x13b/0x144 [] kvm_assign_device+0xba/0x117 [] kvm_vm_ioctl_assigned_device+0x301/0xa47 [] ? kvm_vm_ioctl_assigned_device+0xac/0xa47 [] ? native_sched_clock+0x32/0x6b [] ? sched_clock_cpu+0x45/0xd4 [] ? trace_hardirqs_off+0xd/0xf [] ? local_clock+0x41/0x5a [] ? lock_release_holdtime+0x2c/0x129 [] ? cmpxchg_double_slab+0xd0/0x12b [] ? avc_has_perm_noaudit+0x388/0x399 [] ? native_sched_clock+0x32/0x6b [] ? sched_clock+0x9/0xd [] kvm_vm_ioctl+0x36c/0x3a2 [] ? native_sched_clock+0x32/0x6b [] ? sched_clock+0x9/0xd [] do_vfs_ioctl+0x49e/0x4e4 [] sys_ioctl+0x5a/0x7c [] system_call_fastpath+0x16/0x1b RIP [] put_compound_page+0xd4/0x168 Signed-off-by: Youquan Song Reviewed-by: Andrea Arcangeli Signed-off-by: Andrew Morton --- arch/x86/mm/gup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index ea305856151c..dd74e46828c0 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -201,6 +201,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr, do { VM_BUG_ON(compound_head(page) != head); pages[*nr] = page; + if (PageTail(page)) + get_huge_page_tail(page); (*nr)++; page++; refs++; -- 2.39.5