Re: [PATCH 1/2] virtio: allow drivers to validate features

From	Cornelia Huck <cornelia.huck@de.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] virtio: allow drivers to validate features
Date	2017-03-30 11:10 +0200
Message-ID	<tqEfE-451-17@gated-at.bofh.it> (permalink)
References	<tqpqi-1xr-5@gated-at.bofh.it>
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On Wed, 29 Mar 2017 20:14:44 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> Some drivers can't support all features in all configurations.  At the
> moment we blindly set FEATURES_OK and later FAILED.  Support this better
> by adding a callback drivers can use to do some early checks.

Looks reasonable. Do we need to document that the driver must not do
anything beyond dealing with features and reading the config space that
early?

> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  drivers/virtio/virtio.c | 6 ++++++
>  include/linux/virtio.h  | 1 +
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 400d70b..48230a5 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -232,6 +232,12 @@ static int virtio_dev_probe(struct device *_d)
>  		if (device_features & (1ULL << i))
>  			__virtio_set_bit(dev, i);
>  
> +	if (drv->validate) {
> +		err = drv->validate(dev);
> +		if (err)
> +			goto err;
> +	}
> +
>  	err = virtio_finalize_features(dev);
>  	if (err)
>  		goto err;
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 193fea9..ed04753 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -176,6 +176,7 @@ struct virtio_driver {
>  	unsigned int feature_table_size;
>  	const unsigned int *feature_table_legacy;
>  	unsigned int feature_table_size_legacy;
> +	int (*validate)(struct virtio_device *dev);
>  	int (*probe)(struct virtio_device *dev);
>  	void (*scan)(struct virtio_device *dev);
>  	void (*remove)(struct virtio_device *dev);

Would be good to add some doc; but other members are undocumented here
already...

Thread

[PATCH 1/2] virtio: allow drivers to validate features "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-29 19:20 +0200
  [PATCH 2/2] virtio_net: clear MTU when out of range "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-29 19:20 +0200
  Re: [PATCH 1/2] virtio: allow drivers to validate features Cornelia Huck <cornelia.huck@de.ibm.com> - 2017-03-30 11:10 +0200
    Re: [PATCH 1/2] virtio: allow drivers to validate features "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-30 17:00 +0200
  Re: [PATCH 1/2] virtio: allow drivers to validate features David Miller <davem@davemloft.net> - 2017-03-30 21:50 +0200
    Re: [PATCH 1/2] virtio: allow drivers to validate features "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-31 05:30 +0200

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