On Sun, 3 Jul 2011 15:11:37 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > On Sun, Jul 03, 2011 at 01:52:29PM +0300, Sasha Levin wrote: > > This just leads me to believe that we should either not notify the host, > > or not wait_for_completion() when telling the host. > > Interesting. The spec says > > (a) The driver constructs an array of addresses of memory pages it has > previously given to the balloon, as described above. This descriptor > is added to the deflateq. > (b) If the VIRTIO_BALLOON_F_MUST_TELL_HOST feature is set, > the guest may not use these requested pages until that descriptor in > the deflateq has been used by the device. > (c) Otherwise, the guest may begin to re-use pages previously given to > the balloon before the device has acknowledged their withdrawl. > 21 In this case, deflation advice is merely a courtesy > > This does not discuss the following issue: what happens > if the device never uses the descriptor in the deflateq > and VIRTIO_BALLOON_F_MUST_TELL_HOST is not set? > > Rusty, any comments? The device still *has* a queue. It should process it! The feature should be called VIRTIO_BALLOON_F_ASK_HOST_BEFORE_REUSE. If we didn't want the information at *all*, we would have made the queue not exist in that case... Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
