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author | Andrea Arcangeli <aarcange@redhat.com> | 2013-02-22 15:11:49 -0800 |
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committer | Ingo Molnar <mingo@kernel.org> | 2013-02-24 13:01:44 +0100 |
commit | 954f857187033ee3d3704a8206715cf354c38898 (patch) | |
tree | 0298d5fa15655bcddc19200bc86eed34f34c0ced /arch/x86 | |
parent | 942670d0dc41b5fe9b735c31ca9234d80729bf7e (diff) | |
download | op-kernel-dev-954f857187033ee3d3704a8206715cf354c38898.zip op-kernel-dev-954f857187033ee3d3704a8206715cf354c38898.tar.gz |
Revert "x86, mm: Make spurious_fault check explicitly check explicitly check the PRESENT bit"
I got a report for a minor regression introduced by commit
027ef6c87853b ("mm: thp: fix pmd_present for split_huge_page and
PROT_NONE with THP").
So the problem is, pageattr creates kernel pagetables (pte and
pmds) that breaks pte_present/pmd_present and the patch above
exposed this invariant breakage for pmd_present.
The same problem already existed for the pte and pte_present and
it was fixed by commit 660a293ea9be709 ("x86, mm: Make
spurious_fault check explicitly check the PRESENT bit") (if it
wasn't for that commit, it wouldn't even be a regression). That
fix avoids the pagefault to use pte_present. I could follow
through by stopping using pmd_present/pmd_huge too.
However I think it's more robust to fix pageattr and to clear
the PSE/GLOBAL bitflags too in addition to the present bitflag.
So the kernel page fault can keep using the regular
pte_present/pmd_present/pmd_huge.
The confusion arises because _PAGE_GLOBAL and _PAGE_PROTNONE are
sharing the same bit, and in the pmd case we pretend _PAGE_PSE
to be set only in present pmds (to facilitate split_huge_page
final tlb flush).
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/mm/fault.c | 8 |
1 files changed, 1 insertions, 7 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index fb674fd..2b97525 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -939,14 +939,8 @@ spurious_fault(unsigned long error_code, unsigned long address) if (pmd_large(*pmd)) return spurious_fault_check(error_code, (pte_t *) pmd); - /* - * Note: don't use pte_present() here, since it returns true - * if the _PAGE_PROTNONE bit is set. However, this aliases the - * _PAGE_GLOBAL bit, which for kernel pages give false positives - * when CONFIG_DEBUG_PAGEALLOC is used. - */ pte = pte_offset_kernel(pmd, address); - if (!(pte_flags(*pte) & _PAGE_PRESENT)) + if (!pte_present(*pte)) return 0; ret = spurious_fault_check(error_code, pte); |