On Thu, 13 Nov 2014 13:52:53 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:
typo in subject-prefix: s/virito/virtio/
> Buggy host may advertised buggy host features (a usual case is that host
> advertise a feature whose dependencies were missed). In this case, driver
> should detect and disable the buggy features by itself.
>
> This patch introduces driver specific fix_features() method which is called
> just before features finalizing to detect and disable buggy features
> advertised by host.
So the basic problem this patch fixes is that an individual driver may
only specify a static set of features but cannot specify any
dependencies, right? Adding a sanitizer step makes sense, I guess.
>
> Virtio-net will be the first user.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/virtio/virtio.c | 4 ++++
> include/linux/virtio.h | 1 +
> include/linux/virtio_config.h | 12 ++++++++++++
> 3 files changed, 17 insertions(+)
>
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index df598dd..7001d6e 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -181,6 +181,10 @@ static int virtio_dev_probe(struct device *_d)
> if (device_features & (1 << i))
> set_bit(i, dev->features);
>
> + /* Fix buggy features advertised by host */
> + if (drv->fix_features)
> + drv->fix_features(dev);
I'd probably call this "sanitize_features" instead.
> +
> dev->config->finalize_features(dev);
>
> err = drv->probe(dev);
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 7f4ef66..7bd89ea 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -96,6 +96,18 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
> return test_bit(fbit, vdev->features);
> }
>
> +static inline void virtio_disable_feature(struct virtio_device *vdev,
> + unsigned int fbit)
> +{
> + BUG_ON(fbit >= VIRTIO_TRANSPORT_F_START);
> + BUG_ON(vdev->config->get_status(vdev) &
> + ~(VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER));
When we add virtio-1 support, we can add a check for FEATURES_OK here,
so we're really on the safe side.
> +
> + virtio_check_driver_offered_feature(vdev, fbit);
> +
> + clear_bit(fbit, vdev->features);
> +}
> +
> static inline
> struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
> vq_callback_t *c, const char *n)
The approach looks good to me.
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