The patch titled
Subject: thp: set compound tail page _count to zero
has been added to the -mm tree. Its filename is
thp-set-compound-tail-page-_count-to-zero.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Youquan Song <youquan.song@xxxxxxxxx>
Subject: thp: set compound tail page _count to zero
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 at 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:
[<ffffffff81072f7f>] gup_pud_range+0xb8/0x19d
[<ffffffff8107312f>] get_user_pages_fast+0xcb/0x192
[<ffffffff810bc450>] ? trace_hardirqs_off+0xd/0xf
[<ffffffff81006a24>] hva_to_pfn+0x119/0x2f2
[<ffffffff81006c29>] gfn_to_pfn_memslot+0x2c/0x2e
[<ffffffff8100b909>] kvm_iommu_map_pages+0xfd/0x1c1
[<ffffffff8100ba49>] kvm_iommu_map_memslots+0x7c/0xbd
[<ffffffff8100b9cd>] ? kvm_iommu_map_pages+0x1c1/0x1c1
[<ffffffff8100bb34>] kvm_iommu_map_guest+0xaa/0xbf
[<ffffffff8100aeb0>] kvm_vm_ioctl_assigned_device+0x2ef/0xa47
[<ffffffff8100ac6d>] ? kvm_vm_ioctl_assigned_device+0xac/0xa47
[<ffffffff8104f2a6>] ? native_sched_clock+0x32/0x6b
[<ffffffff810b0c02>] ? sched_clock_cpu+0x45/0xd4
[<ffffffff810bc450>] ? trace_hardirqs_off+0xd/0xf
[<ffffffff810b0cd2>] ? local_clock+0x41/0x5a
[<ffffffff810bc8a1>] ? lock_release_holdtime+0x2c/0x129
[<ffffffff8115762d>] ? cmpxchg_double_slab+0xd0/0x12b
[<ffffffff81248f47>] ? avc_has_perm_noaudit+0x388/0x399
[<ffffffff8104f2a6>] ? native_sched_clock+0x32/0x6b
[<ffffffff8104f2e8>] ? sched_clock+0x9/0xd
[<ffffffff81007dcb>] kvm_vm_ioctl+0x36c/0x3a2
[<ffffffff8104f2a6>] ? native_sched_clock+0x32/0x6b
[<ffffffff8104f2e8>] ? sched_clock+0x9/0xd
[<ffffffff81174b10>] do_vfs_ioctl+0x49e/0x4e4
[<ffffffff81174bb0>] sys_ioctl+0x5a/0x7c
[<ffffffff81500e02>] system_call_fastpath+0x16/0x1b
RIP [<ffffffff81072d13>] gup_huge_pud+0xf2/0x159
Signed-off-by: Youquan Song <youquan.song@xxxxxxxxx>
Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 1 +
mm/page_alloc.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
diff -puN mm/hugetlb.c~thp-set-compound-tail-page-_count-to-zero mm/hugetlb.c
--- a/mm/hugetlb.c~thp-set-compound-tail-page-_count-to-zero
+++ a/mm/hugetlb.c
@@ -576,6 +576,7 @@ static void prep_compound_gigantic_page(
__SetPageHead(page);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
__SetPageTail(p);
+ set_page_count(p, 0);
p->first_page = page;
}
}
diff -puN mm/page_alloc.c~thp-set-compound-tail-page-_count-to-zero mm/page_alloc.c
--- a/mm/page_alloc.c~thp-set-compound-tail-page-_count-to-zero
+++ a/mm/page_alloc.c
@@ -356,8 +356,8 @@ void prep_compound_page(struct page *pag
__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;
}
}
_
Subject: Subject: thp: set compound tail page _count to zero
Patches currently in -mm which might be from youquan.song@xxxxxxxxx are
thp-add-compound-tail-page-_mapcount-when-mapped.patch
thp-set-compound-tail-page-_count-to-zero.patch
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