linux-kernel - Re: [PATCH RFC] virtio_pci: fix virtio spec compliance on restore

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Date:	Wed, 24 Sep 2014 17:57:00 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH RFC] virtio_pci: fix virtio spec compliance on restore

On (Tue) 23 Sep 2014 [13:32:22], Michael S. Tsirkin wrote:
> On restore, virtio pci does the following:
> + set features
> + init vqs etc - device can be used at this point!
> + set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits
> 
> This is in violation of the virtio spec, which
> requires the following order:
> - ACKNOWLEDGE
> - DRIVER
> - init vqs
> - DRIVER_OK
> 
> Cc: stable@...r.kernel.org
> Cc: Amit Shah <amit.shah@...hat.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> 
> Lightly tested.
> Will repost as non-RFC once testing is done, sending
> out now for early flames/comments.

What tests are you running?

> Thanks!
> 
>  drivers/virtio/virtio_pci.c | 36 ++++++++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> index 58f7e45..58cbf6e 100644
> --- a/drivers/virtio/virtio_pci.c
> +++ b/drivers/virtio/virtio_pci.c
> @@ -785,6 +785,7 @@ static int virtio_pci_restore(struct device *dev)
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
>  	struct virtio_driver *drv;
> +	unsigned status = 0;
>  	int ret;
>  
>  	drv = container_of(vp_dev->vdev.dev.driver,
> @@ -795,14 +796,41 @@ static int virtio_pci_restore(struct device *dev)
>  		return ret;
>  
>  	pci_set_master(pci_dev);
> +	/* We always start by resetting the device, in case a previous
> +	 * driver messed it up. */
> +	vp_reset(&vp_dev->vdev);
> +
> +	/* Acknowledge that we've seen the device. */
> +	status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
> +	vp_set_status(&vp_dev->vdev, status);
> +
> +	/* Maybe driver failed before freeze.
> +	 * Restore the failed status, for debugging. */
> +	status |= vp_dev->saved_status & VIRTIO_CONFIG_S_FAILED;
> +	vp_set_status(&vp_dev->vdev, status);
> +
> +	if (!drv)
> +		return 0;
> +
> +	/* We have a driver! */
> +	status |= VIRTIO_CONFIG_S_DRIVER;
> +	vp_set_status(&vp_dev->vdev, status);
> +
>  	vp_finalize_features(&vp_dev->vdev);
>  
> -	if (drv && drv->restore)
> -		ret = drv->restore(&vp_dev->vdev);
> +	if (!drv->restore)
> +		return 0;

So in this case DRIVER_OK will never be set?

> +
> +	ret = drv->restore(&vp_dev->vdev);
> +	if (ret) {
> +		status |= VIRTIO_CONFIG_S_FAILED;
> +		vp_set_status(&vp_dev->vdev, status);
> +		return ret;
> +	}
>  
>  	/* Finally, tell the device we're all set */
> -	if (!ret)
> -		vp_set_status(&vp_dev->vdev, vp_dev->saved_status);
> +	status |= VIRTIO_CONFIG_S_DRIVER_OK;
> +	vp_set_status(&vp_dev->vdev, status);
>  
>  	return ret;
>  }

		Amit
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