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.

v6:
- Based on top of block and net module remove race fix patches

v5:
- Enable virtio device after the driver-specific restore/thaw callbacks are completed.
- Balloon: Don't exit kthread on freeze. It's already frozen by the PM API before invoking the freeze callback, so exiting is pointless.

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 (11):
virtio: pci: switch to new PM API
virtio: pci: add PM notification handlers for restore, freeze, thaw,
poweroff
virtio: console: Move vq and vq buf removal into separate functions
virtio: console: Add freeze and restore handlers to support S4
virtio: blk: Move vq initialization to separate function
virtio: blk: Add freeze, restore handlers to support S4
virtio: net: Move vq initialization into separate function
virtio: net: Move vq and vq buf removal into separate function
virtio: net: Add freeze, restore handlers to support S4
virtio: balloon: Move vq initialization into separate function
virtio: balloon: Add freeze, restore handlers to support S4

 drivers/block/virtio_blk.c      |   63 ++++++++++++++++++--
 drivers/char/virtio_console.c   |  126 ++++++++++++++++++++++++++++++---------
 drivers/net/virtio_net.c        |  113 ++++++++++++++++++++++++++--------
 drivers/virtio/virtio_balloon.c |   95 ++++++++++++++++++++++++------
 drivers/virtio/virtio_pci.c     |  106 +++++++++++++++++++++++++++++++-
 include/linux/virtio.h          |    5 ++
 6 files changed, 426 insertions(+), 82 deletions(-)

1.7.7.4