1. 15 Oct, 2019 1 commit
    • Tom Murphy's avatar
      iommu/amd: Remove unnecessary locking from AMD iommu driver · 37ec8eb8
      Tom Murphy authored
      With or without locking it doesn't make sense for two writers to be
      writing to the same IOVA range at the same time. Even with locking we
      still have a race condition, whoever gets the lock first, so we still
      can't be sure what the result will be. With locking the result will be
      more sane, it will be correct for the last writer, but still useless
      because we can't be sure which writer will get the lock last. It's a
      fundamentally broken design to have two writers writing to the same
      IOVA range at the same time.
      
      So we can remove the locking and work on the assumption that no two
      writers will be writing to the same IOVA range at the same time.
      
      The only exception is when we have to allocate a middle page in the page
      tables, the middle page can cover more than just the IOVA range a writer
      has been allocated. However this isn't an issue in the AMD driver
      because it can atomically allocate middle pages using "cmpxchg64()".
      Signed-off-by: default avatarTom Murphy <murphyt7@tcd.ie>
      Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
      37ec8eb8
  2. 13 Oct, 2019 16 commits
  3. 12 Oct, 2019 23 commits