On 25 July 2013 06:38, Michael S. Tsirkin <m...@redhat.com> wrote: > On Fri, Jul 12, 2013 at 09:36:57PM +0100, Peter Maydell wrote: >> The MMIO virtio transport spec allows the guest to tell the host how >> large the queue size is. Add virtio_queue_set_num() function which >> implements this in the QEMU common virtio support code. >> >> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> > > Probably needs to go back to default value on reset?
Tricky, since the default value is "whatever was passed to virtio_add_queue()" and we don't save that anywhere. For virtio-mmio it is a guest bug to fail to write to the QueueNum register, so the current behaviour is not out of specification (and not harmful either AFAICT). I guess we could add a vring.defaultnum, which would be set by virtio_add_queue/virtio_del_queue, and have reset copy defaultnum into num. No migration needed for defaultnum because it's always the same for a particular qemu config. > Need to migrate? It's already migrated (though I'm not entirely sure why). > Is the default value a max legal value? If yes probably a good > idea to enforce this. virtio_add_queue() already enforces this -- it will abort() if you try to set up a queue with a default size greater than VIRTQUEUE_MAX_SIZE. thanks -- PMM
