Re: [PATCH V13 6/6] docs: sample driver to demonstrate how to implement virtio-mdev framework

Cornelia Huck
2019-11-18T15:45:10Z

On Mon, 18 Nov 2019 18:59:23 +0800
Jason Wang <jasowang@redhat.com> wrote:

[Note: I have not looked into the reworked architecture of this *at all*
so far; just something that I noted...]

> This sample driver creates mdev device that simulate virtio net device
> over virtio mdev transport. The device is implemented through vringh
> and workqueue. A device specific dma ops is to make sure HVA is used
> directly as the IOVA. This should be sufficient for kernel virtio
> driver to work.
>
> Only 'virtio' type is supported right now. I plan to add 'vhost' type
> on top which requires some virtual IOMMU implemented in this sample
> driver.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> MAINTAINERS | 1 +
> samples/Kconfig | 10 +
> samples/vfio-mdev/Makefile | 1 +
> samples/vfio-mdev/mvnet_loopback.c | 690 +++++++++++++++++++++++++++++
> 4 files changed, 702 insertions(+)
> create mode 100644 samples/vfio-mdev/mvnet_loopback.c
>

> +static struct mvnet_dev {
> + struct class *vd_class;
> + struct idr vd_idr;
> + struct device dev;
> +} mvnet_dev;

This structure embeds a struct device (a reference-counted structure),
yet it is a static variable. This is giving a bad example to potential
implementers; just allocate it dynamically.

> +static void mvnet_device_release(struct device *dev)
> +{
> + dev_dbg(dev, "mvnet: released\n");

And that also means you need a proper release function here, of
course.

> +}