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

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Date:   Tue, 19 Nov 2019 11:04:51 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
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Subject: Re: [PATCH V13 6/6] docs: sample driver to demonstrate how to
 implement virtio-mdev framework


On 2019/11/18 下午11:45, Cornelia Huck wrote:
> On Mon, 18 Nov 2019 18:59:23 +0800
> Jason Wang <jasowang@...hat.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@...hat.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.


Yes, as spotted by Greg.


>
>> +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.


Right.

Thanks


>
>> +}