[PATCH v21 QEMU 0/5] virtio-balloon: add support for free page reporting

[Alexander Duyck <alexander.duyck@gmail.com>]

This series provides an asynchronous means of reporting free guest pages
to QEMU through virtio-balloon so that the memory associated with those
pages can be dropped and reused by other processes and/or guests on the
host. Using this it is possible to avoid unnecessary I/O to disk and
greatly improve performance in the case of memory overcommit on the host.

As of April 7th this functionality has been enabled in Linus's kernel
tree[1] and so I am submitting the QEMU pieces for inclusion.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b0c504f154718904ae49349147e3b7e6ae91ffdc

Changes from v17:
Fixed typo in patch 1 title
Addressed white-space issues reported via checkpatch
Added braces {} for two if statements to match expected coding style

Changes from v18:
Updated patches 2 and 3 based on input from dhildenb
Added comment to patch 2 describing what keeps us from reporting a bad page
Added patch to address issue with ROM devices being directly writable

Changes from v19:
Added std-headers change to match changes pushed for linux kernel headers
Added patch to remove "report" from page hinting code paths
Updated comment to better explain why we disable hints w/ page poisoning
Removed code that was modifying config size for poison vs hinting
Dropped x-page-poison property
Added code to bounds check the reported region vs the RAM block
Dropped patch for ROM devices as that was already pulled in by Paolo

Changes from v20:
Rearranged patches to push Linux header sync patches to front
Removed association between free page hinting and VIRTIO_BALLOON_F_PAGE_POISON
Added code to enable VIRTIO_BALLOON_F_PAGE_POISON if page reporting is enabled
Fixed possible resource leak if poison or qemu_balloon_is_inhibited return true
Updated cover page comments

---

Alexander Duyck (5):
      linux-headers: Update to allow renaming of free_page_report_cmd_id
      linux-headers: update to contain virito-balloon free page reporting
      virtio-balloon: Replace free page hinting references to 'report' with 'hint'
      virtio-balloon: Implement support for page poison tracking feature
      virtio-balloon: Provide an interface for free page reporting


 hw/virtio/virtio-balloon.c                      |  151 +++++++++++++++++------
 include/hw/virtio/virtio-balloon.h              |   23 ++--
 include/standard-headers/linux/virtio_balloon.h |   12 ++
 3 files changed, 136 insertions(+), 50 deletions(-)

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