3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mel Gorman <[email protected]> commit 29c7787075c92ca8af353acd5301481e6f37082f upstream. David Vrabel identified a regression when using automatic NUMA balancing under Xen whereby page table entries were getting corrupted due to the use of native PTE operations. Quoting him Xen PV guest page tables require that their entries use machine addresses if the preset bit (_PAGE_PRESENT) is set, and (for successful migration) non-present PTEs must use pseudo-physical addresses. This is because on migration MFNs in present PTEs are translated to PFNs (canonicalised) so they may be translated back to the new MFN in the destination domain (uncanonicalised). pte_mknonnuma(), pmd_mknonnuma(), pte_mknuma() and pmd_mknuma() set and clear the _PAGE_PRESENT bit using pte_set_flags(), pte_clear_flags(), etc. In a Xen PV guest, these functions must translate MFNs to PFNs when clearing _PAGE_PRESENT and translate PFNs to MFNs when setting _PAGE_PRESENT. His suggested fix converted p[te|md]_[set|clear]_flags to using paravirt-friendly ops but this is overkill. He suggested an alternative of using p[te|md]_modify in the NUMA page table operations but this is does more work than necessary and would require looking up a VMA for protections. This patch modifies the NUMA page table operations to use paravirt friendly operations to set/clear the flags of interest. Unfortunately this will take a performance hit when updating the PTEs on CONFIG_PARAVIRT but I do not see a way around it that does not break Xen. Signed-off-by: Mel Gorman <[email protected]> Acked-by: David Vrabel <[email protected]> Tested-by: David Vrabel <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Anvin <[email protected]> Cc: Fengguang Wu <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Steven Noonan <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Srikar Dronamraju <[email protected]> Cc: Cyrill Gorcunov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- include/asm-generic/pgtable.h | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -680,24 +680,35 @@ static inline int pmd_numa(pmd_t pmd) #ifndef pte_mknonnuma static inline pte_t pte_mknonnuma(pte_t pte) { - pte = pte_clear_flags(pte, _PAGE_NUMA); - return pte_set_flags(pte, _PAGE_PRESENT|_PAGE_ACCESSED); + pteval_t val = pte_val(pte); + + val &= ~_PAGE_NUMA; + val |= (_PAGE_PRESENT|_PAGE_ACCESSED); + return __pte(val); } #endif #ifndef pmd_mknonnuma static inline pmd_t pmd_mknonnuma(pmd_t pmd) { - pmd = pmd_clear_flags(pmd, _PAGE_NUMA); - return pmd_set_flags(pmd, _PAGE_PRESENT|_PAGE_ACCESSED); + pmdval_t val = pmd_val(pmd); + + val &= ~_PAGE_NUMA; + val |= (_PAGE_PRESENT|_PAGE_ACCESSED); + + return __pmd(val); } #endif #ifndef pte_mknuma static inline pte_t pte_mknuma(pte_t pte) { - pte = pte_set_flags(pte, _PAGE_NUMA); - return pte_clear_flags(pte, _PAGE_PRESENT); + pteval_t val = pte_val(pte); + + val &= ~_PAGE_PRESENT; + val |= _PAGE_NUMA; + + return __pte(val); } #endif @@ -716,8 +727,12 @@ static inline void ptep_set_numa(struct #ifndef pmd_mknuma static inline pmd_t pmd_mknuma(pmd_t pmd) { - pmd = pmd_set_flags(pmd, _PAGE_NUMA); - return pmd_clear_flags(pmd, _PAGE_PRESENT); + pmdval_t val = pmd_val(pmd); + + val &= ~_PAGE_PRESENT; + val |= _PAGE_NUMA; + + return __pmd(val); } #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
