netdev - Re: [PATCH v12 05/13] vdpa: Add reset callback in vdpa_config

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Date:   Mon, 6 Sep 2021 01:54:46 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     jasowang@...hat.com, stefanha@...hat.com, sgarzare@...hat.com,
        parav@...dia.com, hch@...radead.org,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.com,
        dan.carpenter@...cle.com, joro@...tes.org,
        gregkh@...uxfoundation.org, zhe.he@...driver.com,
        xiaodong.liu@...el.com, joe@...ches.com, robin.murphy@....com,
        will@...nel.org, john.garry@...wei.com, songmuchun@...edance.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 05/13] vdpa: Add reset callback in vdpa_config_ops

On Mon, Aug 30, 2021 at 10:17:29PM +0800, Xie Yongji wrote:
> This adds a new callback to support device specific reset
> behavior. The vdpa bus driver will call the reset function
> instead of setting status to zero during resetting.
> 
> Signed-off-by: Xie Yongji <xieyongji@...edance.com>

This does gloss over a significant change though:

> @@ -348,12 +352,12 @@ 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)
> +static inline int vdpa_reset(struct vdpa_device *vdev)
>  {
>  	const struct vdpa_config_ops *ops = vdev->config;
>  
>  	vdev->features_valid = false;
> -	ops->set_status(vdev, 0);
> +	return ops->reset(vdev);
>  }
>  
>  static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features)

Unfortunately this breaks virtio_vdpa:


static void virtio_vdpa_reset(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);

        vdpa_reset(vdpa);
}


and there's no easy way to fix this, kernel can't recover
from a reset failure e.g. during driver unbind.

Find a way to disable virtio_vdpa for now?

> -- 
> 2.11.0