virtio: s4 support

Hi,

These patches add support for S4 to virtio (pci) and all drivers.

For each driver, all vqs are removed before hibernation, and then
re-created after restore.  Some driver-specific uninit and init work
is also done in the freeze and restore functions.

All the drivers in testing work fine:

* virtio-blk is used for the only disk in the VM, IO works fine before
  and after.  'dd if=/dev/zero of=/tmp/bigfile bs=1024 count=200000'
  across S4 gives same sha1sum for the file in the guest as well as
  one that's created without invoking S4.

* virtio-console: port IO keeps working fine before and after.
  * If a port is waiting for data from the host (blocking read(2)
    call), this works fine in both the cases: host-side connection is
    available or unavailable after resume.  In case the host-side
    connection isn't available, the blocking call is terminated.  If
    it is available, the call continues to remain in blocked state
    till further data arrives.

* virtio-net: ping remains active across S4.

* virtio-balloon: Works fine before and after.  Forgets the ballooned
  value across S4 (see details in commit log). Maintains ballooned
  value on failed freeze.

All of these tests are run in parallel.

I have some more tests lined up on similar lines above.  I'll reply
here if something breaks.

Please review and apply if appropriate,

v4:
 - Disable / enable napi across S4 (Michael S. Tsirkin)
 - Balloon: lots of improvements (I had neglected this driver thinking
   it was a simple one, but this one needed the most thought!  Check
   the commit log for patch 12 for details.)
 - Net, Blk: Reset device as the first operation on freeze

v3:
 - Reset vqs before deleting them (Sasha Levin)
 - Flush block queue before freeze (Rusty)
 - Detach netdev before freeze (Michael S. Tsirkin)

v2:
 - fix checkpatch errors/warnings

Amit Shah (12):
  virtio: pci: switch to new PM API
  virtio: pci: add PM notification handlers for restore, freeze, thaw,
    poweroff
  virtio: console: Move out vq and vq buf removal into separate
    functions
  virtio: console: Add freeze and restore handlers to support S4
  virtio: blk: Move out vq initialization to separate function
  virtio: blk: Add freeze, restore handlers to support S4
  virtio: net: Move out vq initialization into separate function
  virtio: net: Move out vq and vq buf removal into separate function
  virtio: net: Add freeze, restore handlers to support S4
  virtio: balloon: ensure thread exists before stopping it
  virtio: balloon: Move out vq initialization into separate function
  virtio: balloon: Add freeze, restore handlers to support S4

 drivers/block/virtio_blk.c      |   57 +++++++++++++++--
 drivers/char/virtio_console.c   |  126 +++++++++++++++++++++++++++++--------
 drivers/net/virtio_net.c        |  102 ++++++++++++++++++++++--------
 drivers/virtio/virtio_balloon.c |  131 +++++++++++++++++++++++++++++++++------
 drivers/virtio/virtio_pci.c     |  101 +++++++++++++++++++++++++++++-
 include/linux/virtio.h          |    5 ++
 6 files changed, 439 insertions(+), 83 deletions(-)

-- 
1.7.7.3

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