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SubjectRe: [PATCH v2 19/24] vdpa: make sure set_features in invoked for legacy
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On 2020/8/4 上午5:00, Michael S. Tsirkin wrote:
> Some legacy guests just assume features are 0 after reset.
> We detect that config space is accessed before features are
> set and set features to 0 automatically.
> Note: some legacy guests might not even access config space, if this is
> reported in the field we might need to catch a kick to handle these.


I wonder whether it's easier to just support modern device?

Thanks


>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> drivers/vdpa/vdpa.c | 1 +
> include/linux/vdpa.h | 34 ++++++++++++++++++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index de211ef3738c..7105265e4793 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -96,6 +96,7 @@ struct vdpa_device *__vdpa_alloc_device(struct device *parent,
> vdev->dev.release = vdpa_release_dev;
> vdev->index = err;
> vdev->config = config;
> + vdev->features_valid = false;
>
> err = dev_set_name(&vdev->dev, "vdpa%u", vdev->index);
> if (err)
> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> index 239db794357c..29b8296f1414 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -33,12 +33,14 @@ struct vdpa_notification_area {
> * @dma_dev: the actual device that is performing DMA
> * @config: the configuration ops for this device.
> * @index: device index
> + * @features_valid: were features initialized? for legacy guests
> */
> struct vdpa_device {
> struct device dev;
> struct device *dma_dev;
> const struct vdpa_config_ops *config;
> unsigned int index;
> + bool features_valid;
> };
>
> /**
> @@ -266,4 +268,36 @@ static inline struct device *vdpa_get_dma_dev(struct vdpa_device *vdev)
> {
> return vdev->dma_dev;
> }
> +
> +static inline void vdpa_reset(struct vdpa_device *vdev)
> +{
> + const struct vdpa_config_ops *ops = vdev->config;
> +
> + vdev->features_valid = false;
> + ops->set_status(vdev, 0);
> +}
> +
> +static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features)
> +{
> + const struct vdpa_config_ops *ops = vdev->config;
> +
> + vdev->features_valid = true;
> + return ops->set_features(vdev, features);
> +}
> +
> +
> +static inline void vdpa_get_config(struct vdpa_device *vdev, unsigned offset,
> + void *buf, unsigned int len)
> +{
> + const struct vdpa_config_ops *ops = vdev->config;
> +
> + /*
> + * Config accesses aren't supposed to trigger before features are set.
> + * If it does happen we assume a legacy guest.
> + */
> + if (!vdev->features_valid)
> + vdpa_set_features(vdev, 0);
> + ops->get_config(vdev, offset, buf, len);
> +}
> +
> #endif /* _LINUX_VDPA_H */

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