linux/drivers/virtio, branch v3.3

virtio: balloon: leak / fill balloon across S4

2012-02-29T22:58:41Z

commit e562966dbaf49e7804097cd991e5d3a8934fc148 added support for S4 to the balloon driver. The freeze function did nothing to free the pages, since reclaiming the pages from the host to immediately give them back (if S4 was successful) seemed wasteful. Also, if S4 wasn't successful, the guest would have to re-fill the balloon. On restore, the pages were supposed to be marked freed and the free page counters were incremented to reflect the balloon was totally deflated. However, this wasn't done right. The pages that were earlier taken away from the guest during a balloon inflation operation were just shown as used pages after a successful restore from S4. Just a fancy way of leaking lots of memory. Instead of trying that, just leak the balloon on freeze and fill it on restore/thaw paths. This works properly now. The optimisation to not leak can be added later on after a bit of refactoring of the code. Signed-off-by: Amit Shah Signed-off-by: Rusty Russell

virtio: correct the memory barrier in virtqueue_kick_prepare()

2012-01-27T21:40:23Z

Use virtio_mb() to make sure the available index to be exposed before checking the the avail event. Otherwise we may get stale value of avail event in guest and never kick the host after. Note: this fixes a bug introduced by ee7cd8981e15bcb365fc762afe3fc47b8242f630. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: Rusty Russell Cc: stable@kernel.org

virtio: fix typos of memory barriers

2012-01-27T21:40:22Z

Note: this fixes a bug introduced recently in 7b21e34fd1c272e3a8c3846168f2f6287a4cd72b. Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: Rusty Russell

virtio: balloon: Add freeze, restore handlers to support S4

2012-01-12T05:14:47Z

Handling balloon hibernate / restore is tricky. If the balloon was inflated before going into the hibernation state, upon resume, the host will not have any memory of that. Any pages that were passed on to the host earlier would most likely be invalid, and the host will have to re-balloon to the previous value to get in the pre-hibernate state. So the only sane thing for the guest to do here is to discard all the pages that were put in the balloon. When to discard the pages is the next question. One solution is to deflate the balloon just before writing the image to the disk (in the freeze() PM callback). However, asking for pages from the host just to discard them immediately after seems wasteful of resources. Hence, it makes sense to do this by just fudging our counters soon after wakeup. This means we don't deflate the balloon before sleep, and also don't put unnecessary pressure on the host. This also helps in the thaw case: if the freeze fails for whatever reason, the balloon should continue to remain in the inflated state. This was tested by issuing 'swapoff -a' and trying to go into the S4 state. That fails, and the balloon stays inflated, as expected. Both the host and the guest are happy. Finally, in the restore() callback, we empty the list of pages that were previously given off to the host, add the appropriate number of pages to the totalram_pages counter, reset the num_pages counter to 0, and all is fine. As a last step, delete the vqs on the freeze callback to prepare for hibernation, and re-create them in the restore and thaw callbacks to resume normal operation. The kthread doesn't race with any operations here, since it's frozen before the freeze() call and is thawed after the thaw() and restore() callbacks, so we're safe with that. Signed-off-by: Amit Shah Signed-off-by: Rusty Russell

virtio: balloon: Move vq initialization into separate function

2012-01-12T05:14:46Z

The probe and PM restore functions will share this code. Signed-off-by: Amit Shah Signed-off-by: Rusty Russell

virtio: pci: add PM notification handlers for restore, freeze, thaw, poweroff

2012-01-12T05:14:44Z

Handle thaw, restore and freeze notifications from the PM core. Expose these to individual virtio drivers that can quiesce and resume vq operations. For drivers not implementing the thaw() method, use the restore method instead. These functions also save device-specific data so that the device can be put in pre-suspend state after resume, and disable and enable the PCI device in the freeze and resume functions, respectively. Signed-off-by: Amit Shah Signed-off-by: Rusty Russell

virtio: pci: switch to new PM API

2012-01-12T05:14:44Z

The older PM API doesn't have a way to get notifications on hibernate events. Switch to the newer one that gives us those notifications. Signed-off-by: Amit Shah Signed-off-by: Rusty Russell

virtio: add debugging if driver doesn't kick.

2012-01-12T05:14:43Z

Under the existing #ifdef DEBUG, check that they don't have more than 1/10 of a second between an add_buf() and a virtqueue_notify()/virtqueue_kick_prepare() call. We could get false positives on a really busy system, but good for development. Signed-off-by: Rusty Russell

virtio: expose added descriptors immediately.

2012-01-12T05:14:43Z

A virtio driver does virtqueue_add_buf() multiple times before finally calling virtqueue_kick(); previously we only exposed the added buffers in the virtqueue_kick() call. This means we don't need a memory barrier in virtqueue_add_buf(), but it reduces concurrency as the device (ie. host) can't see the buffers until the kick. In the unusual (but now possible) case where a driver does add_buf() and get_buf() without doing a kick, we do need to insert one before our counter wraps. Otherwise we could wrap num_added, and later on not realize that we have passed the marker where we should have kicked. Signed-off-by: Rusty Russell

virtio: avoid modulus operation.

2012-01-12T05:14:43Z

Since we know vq->vring.num is a power of 2, modulus is lazy (it's asserted in vring_new_virtqueue()). Signed-off-by: Rusty Russell