netdev - Re: [PATCH V2 5/5] vdpasim: vDPA device simulator

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Date:   Wed, 12 Feb 2020 16:27:16 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     mst@...hat.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        tiwei.bie@...el.com, maxime.coquelin@...hat.com,
        cunming.liang@...el.com, zhihong.wang@...el.com,
        rob.miller@...adcom.com, xiao.w.wang@...el.com,
        haotian.wang@...ive.com, lingshan.zhu@...el.com,
        eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
        kevin.tian@...el.com, stefanha@...hat.com, rdunlap@...radead.org,
        hch@...radead.org, aadam@...hat.com, jiri@...lanox.com,
        shahafs@...lanox.com, hanand@...inx.com, mhabets@...arflare.com
Subject: Re: [PATCH V2 5/5] vdpasim: vDPA device simulator


On 2020/2/11 下午9:52, Jason Gunthorpe wrote:
> On Mon, Feb 10, 2020 at 11:56:08AM +0800, Jason Wang wrote:
>> +
>> +static struct vdpasim *vdpasim_create(void)
>> +{
>> +	struct vdpasim *vdpasim;
>> +	struct virtio_net_config *config;
>> +	struct vdpa_device *vdpa;
>> +	struct device *dev;
>> +	int ret = -ENOMEM;
>> +
>> +	vdpasim = kzalloc(sizeof(*vdpasim), GFP_KERNEL);
>> +	if (!vdpasim)
>> +		goto err_vdpa_alloc;
>> +
>> +	vdpasim->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
>> +	if (!vdpasim->buffer)
>> +		goto err_buffer_alloc;
>> +
>> +	vdpasim->iommu = vhost_iotlb_alloc(2048, 0);
>> +	if (!vdpasim->iommu)
>> +		goto err_iotlb;
>> +
>> +	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);
>> +
>> +	vdpa = &vdpasim->vdpa;
>> +	vdpa->dev.release = vdpasim_release_dev;
> The driver should not provide the release function.
>
> Again the safest model is 'vdpa_alloc_device' which combines the
> kzalloc and the vdpa_init_device() and returns something that is
> error unwound with put_device()
>
> The subsystem owns the release and does the kfree and other cleanup
> like releasing the IDA.


So I think if we agree bus instead of class is used. vDPA bus can 
provide a release function in vdpa_alloc_device()?


>
>> +	vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
>> +	vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);
>> +
>> +	dev = &vdpa->dev;
>> +	dev->coherent_dma_mask = DMA_BIT_MASK(64);
>> +	set_dma_ops(dev, &vdpasim_dma_ops);
>> +
>> +	ret = vdpa_init_device(vdpa, &vdpasim_dev->dev, dev,
>> +			       &vdpasim_net_config_ops);
>> +	if (ret)
>> +		goto err_init;
>> +
>> +	ret = vdpa_register_device(vdpa);
>> +	if (ret)
>> +		goto err_register;
> See? This error unwind is now all wrong:
>
>> +
>> +	return vdpasim;
>> +
>> +err_register:
>> +	put_device(&vdpa->dev);
> Double put_device


Yes.


>
>> +err_init:
>> +	vhost_iotlb_free(vdpasim->iommu);
>> +err_iotlb:
>> +	kfree(vdpasim->buffer);
>> +err_buffer_alloc:
>> +	kfree(vdpasim);
> kfree after vdpa_init_device() is incorrect, as the put_device now
> does kfree via release


Ok, will fix.


>
>> +static int __init vdpasim_dev_init(void)
>> +{
>> +	struct device *dev;
>> +	int ret = 0;
>> +
>> +	vdpasim_dev = kzalloc(sizeof(*vdpasim_dev), GFP_KERNEL);
>> +	if (!vdpasim_dev)
>> +		return -ENOMEM;
>> +
>> +	dev = &vdpasim_dev->dev;
>> +	dev->release = vdpasim_device_release;
>> +	dev_set_name(dev, "%s", VDPASIM_NAME);
>> +
>> +	ret = device_register(&vdpasim_dev->dev);
>> +	if (ret)
>> +		goto err_register;
>> +
>> +	if (!vdpasim_create())
>> +		goto err_register;
> Wrong error unwind here too


Will fix.

Thanks


>
>> +	return 0;
>> +
>> +err_register:
>> +	kfree(vdpasim_dev);
>> +	vdpasim_dev = NULL;
>> +	return ret;
>> +}
> Jason
>