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

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Date:   Fri, 21 Feb 2020 15:57:29 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     "mst@...hat.com" <mst@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "tiwei.bie@...el.com" <tiwei.bie@...el.com>,
        "maxime.coquelin@...hat.com" <maxime.coquelin@...hat.com>,
        "cunming.liang@...el.com" <cunming.liang@...el.com>,
        "zhihong.wang@...el.com" <zhihong.wang@...el.com>,
        "rob.miller@...adcom.com" <rob.miller@...adcom.com>,
        "xiao.w.wang@...el.com" <xiao.w.wang@...el.com>,
        "haotian.wang@...ive.com" <haotian.wang@...ive.com>,
        "lingshan.zhu@...el.com" <lingshan.zhu@...el.com>,
        "eperezma@...hat.com" <eperezma@...hat.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        Parav Pandit <parav@...lanox.com>,
        "kevin.tian@...el.com" <kevin.tian@...el.com>,
        "stefanha@...hat.com" <stefanha@...hat.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "aadam@...hat.com" <aadam@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Shahaf Shuler <shahafs@...lanox.com>,
        "hanand@...inx.com" <hanand@...inx.com>,
        "mhabets@...arflare.com" <mhabets@...arflare.com>
Subject: 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:
>> +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.


>> +	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.


>
>> +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
>