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| author |   Gerald Schaefer <gerald.schaefer@de.ibm.com> | 2020-05-06 13:04:07 +0200 |
|---|---|---|
| committer |   Vasily Gorbik <gor@linux.ibm.com> | 2020-05-20 10:13:27 +0200 |
| commit | ac8372f3b4e41015549b331a4f350224661e7fc6 (patch) | |
| tree | 80c620f663dddc5c60964399729f0bbed817546e | |
| parent | s390/kexec_file: fix initrd location for kdump kernel (diff) | |
| download | linux-dev-ac8372f3b4e41015549b331a4f350224661e7fc6.tar.xz linux-dev-ac8372f3b4e41015549b331a4f350224661e7fc6.zip | |
s390/mm: fix set_huge_pte_at() for empty ptes
On s390, the layout of normal and large ptes (i.e. pmds/puds) differs.
Therefore, set_huge_pte_at() does a conversion from a normal pte to
the corresponding large pmd/pud. So, when converting an empty pte, this
should result in an empty pmd/pud, which would return true for
pmd/pud_none().
However, after conversion we also mark the pmd/pud as large, and
therefore present. For empty ptes, this will result in an empty pmd/pud
that is also marked as large, and pmd/pud_none() would not return true.
There is currently no issue with this behaviour, as set_huge_pte_at()
does not seem to be called for empty ptes. It would be valid though, so
let's fix this by not marking empty ptes as large in set_huge_pte_at().
This was found by testing a patch from from Anshuman Khandual, which is
currently discussed on LKML ("mm/debug: Add more arch page table helper
tests").
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
| -rw-r--r-- | arch/s390/mm/hugetlbpage.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/s390/mm/hugetlbpage.c b/arch/s390/mm/hugetlbpage.c index f01daddcbc5e..4632d4e26b66 100644 --- a/arch/s390/mm/hugetlbpage.c +++ b/arch/s390/mm/hugetlbpage.c @@ -159,10 +159,13 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, rste &= ~_SEGMENT_ENTRY_NOEXEC; /* Set correct table type for 2G hugepages */ - if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) - rste |= _REGION_ENTRY_TYPE_R3 | _REGION3_ENTRY_LARGE; - else + if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) { + if (likely(pte_present(pte))) + rste |= _REGION3_ENTRY_LARGE; + rste |= _REGION_ENTRY_TYPE_R3; + } else if (likely(pte_present(pte))) rste |= _SEGMENT_ENTRY_LARGE; + clear_huge_pte_skeys(mm, rste); pte_val(*ptep) = rste; } |