Re: [PATCH v6 09/17] virtio: add minimal support for virtqueues

[Paolo Bonzini <pbonzini@redhat.com>]

Il 11/07/2014 11:23, Paolo Bonzini ha scritto:
>
>> +static struct virtqueue *vm_setup_vq(struct virtio_device *vdev,
>> +                     unsigned index,
>> +                     void (*callback)(struct virtqueue *vq),
>> +                     const char *name)
>> +{
>> +    struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
>> +    struct vring_virtqueue *vq;
>> +    void *queue;
>> +    unsigned num = VIRTIO_MMIO_QUEUE_NUM_MIN;
>> +
>> +    vq = alloc(sizeof(*vq));
>
> You can move the allocation of vq to vm_find_vqs (interleaving alloc and
> alloc_aligned causes some fragmentation), allocating a single block
> instead of one per vq.

... or even use static storage for the "struct virtqueue".  You can just 
merge "struct vring_virtqueue" and "struct virtqueue", as the idea of 
other virtqueue transport never materialized.  Then:

+static struct virtqueue in_vq;
+static struct virtqueue out_vq;
+
  void chr_testdev_init(void)
  {
  	const char *io_names[] = { "input", "output" };
-	struct virtqueue *vqs[2];
+	struct virtqueue *vqs[2] = { &in_vq, &out_vq };
  	int ret;

  	vcon = virtio_bind(VIRTIO_ID_CONSOLE);
  	if (vcon == NULL) {
  		printf("%s: %s: can't find a virtio-console\n",
  				__func__, TESTDEV_NAME);
  		return;
  	}

  	ret = vcon->config->find_vqs(vcon, 2, vqs, NULL, io_names);
  	if (ret < 0) {
  		printf("%s: %s: can't init virtqueues\n",
  				__func__, TESTDEV_NAME);
  		vcon = NULL;
  		return;
  	}

-	in_vq = vqs[0];
-	out_vq = vqs[1];
  }

Paolo