Re: [PATCH V4 5/5] vdpasim: vDPA device simulator

On 2020/2/20 下午11:12, Jason Gunthorpe wrote:

On Thu, Feb 20, 2020 at 02:11:41PM +0800, Jason Wang wrote:

quoted

+static void vdpasim_device_release(struct device *dev)
+{
+	struct vdpasim *vdpasim = dev_to_sim(dev);
+
+	cancel_work_sync(&vdpasim->work);
+	kfree(vdpasim->buffer);
+	vhost_iotlb_free(vdpasim->iommu);
+	kfree(vdpasim);
+}
+
+static struct vdpasim *vdpasim_create(void)
+{
+	struct virtio_net_config *config;
+	struct vhost_iotlb *iommu;
+	struct vdpasim *vdpasim;
+	struct device *dev;
+	void *buffer;
+	int ret = -ENOMEM;
+
+	iommu = vhost_iotlb_alloc(2048, 0);
+	if (!iommu)
+		goto err;
+
+	buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buffer)
+		goto err_buffer;
+
+	vdpasim = kzalloc(sizeof(*vdpasim), GFP_KERNEL);
+	if (!vdpasim)
+		goto err_alloc;
+
+	vdpasim->buffer = buffer;
+	vdpasim->iommu = iommu;
+
+	config = &vdpasim->config;
+	config->mtu = 1500;
+	config->status = VIRTIO_NET_S_LINK_UP;
+	eth_random_addr(config->mac);
+
+	INIT_WORK(&vdpasim->work, vdpasim_work);
+	spin_lock_init(&vdpasim->lock);
+
+	vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
+	vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);
+
+	dev = &vdpasim->dev;
+	dev->release = vdpasim_device_release;
+	dev->coherent_dma_mask = DMA_BIT_MASK(64);
+	set_dma_ops(dev, &vdpasim_dma_ops);
+	dev_set_name(dev, "%s", VDPASIM_NAME);
+
+	ret = device_register(&vdpasim->dev);
+	if (ret)
+		goto err_init;

It is a bit weird to be creating this dummy parent, couldn't this be
done by just passing a NULL parent to vdpa_alloc_device, doing
set_dma_ops() on the vdpasim->vdpa->dev and setting dma_device to
vdpasim->vdpa->dev ?

I think it works.

quoted

+	vdpasim->vdpa = vdpa_alloc_device(dev, dev, &vdpasim_net_config_ops);
+	if (ret)
+		goto err_vdpa;
+	ret = vdpa_register_device(vdpasim->vdpa);
+	if (ret)
+		goto err_register;
+
+	return vdpasim;
+
+err_register:
+	put_device(&vdpasim->vdpa->dev);
+err_vdpa:
+	device_del(&vdpasim->dev);
+	goto err;
+err_init:
+	put_device(&vdpasim->dev);
+	goto err;

If you do the vdmasim alloc first, and immediately do
device_initialize() then all the failure paths can do put_device
instead of having this ugly goto unwind split. Just check for
vdpasim->iommu == NULL during release.

Yes, that looks simpler.

quoted

+static int __init vdpasim_dev_init(void)
+{
+	vdpasim_dev = vdpasim_create();
+
+	if (!IS_ERR(vdpasim_dev))
+		return 0;
+
+	return PTR_ERR(vdpasim_dev);
+}
+
+static int vdpasim_device_remove_cb(struct device *dev, void *data)
+{
+	struct vdpa_device *vdpa = dev_to_vdpa(dev);
+
+	vdpa_unregister_device(vdpa);
+
+	return 0;
+}
+
+static void __exit vdpasim_dev_exit(void)
+{
+	device_for_each_child(&vdpasim_dev->dev, NULL,
+			      vdpasim_device_remove_cb);

Why the loop? There is only one device, and it is in the global
varaible vdmasim_dev ?

Not necessary but doesn't harm, will remove this.

Thanks

Jason

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