1. 09 Jun, 2014 36 commits
  2. 09 May, 2014 1 commit
    • Mel Gorman's avatar
      mm: use paravirt friendly ops for NUMA hinting ptes · dec1d8e2
      Mel Gorman authored
      commit 29c77870 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: default avatarMel Gorman <mgorman@suse.de>
      Acked-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Tested-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Peter Anvin <hpa@zytor.com>
      Cc: Fengguang Wu <fengguang.wu@intel.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Steven Noonan <steven@uplinklabs.net>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Cc: Cyrill Gorcunov <gorcunov@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      BugLink: http://bugs.launchpad.net/bugs/1313450
      Cc: Stefan Bader <stefan.bader@canonical.com>
      Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
      dec1d8e2
  3. 08 May, 2014 1 commit
  4. 07 May, 2014 1 commit
  5. 06 May, 2014 1 commit