linux-kernel - Re: [PATCH V1] vdpa: suspend and resume require DRIVER

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Date: Mon, 12 Feb 2024 03:19:39 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Steve Sistare <steven.sistare@...cle.com>
Cc: virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Jason Wang <jasowang@...hat.com>,
	Si-Wei Liu <si-wei.liu@...cle.com>,
	Eugenio Perez Martin <eperezma@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH V1] vdpa: suspend and resume require DRIVER_OK

On Fri, Feb 09, 2024 at 02:29:59PM -0800, Steve Sistare wrote:
> Calling suspend or resume requires VIRTIO_CONFIG_S_DRIVER_OK, for all
> vdpa devices.
> 
> Suggested-by: Eugenio Perez Martin <eperezma@...hat.com>"
> Signed-off-by: Steve Sistare <steven.sistare@...cle.com>

I don't think failing suspend or resume makes sense though -
e.g. practically failing suspend will just prevent sleeping I think -
why should guest not having driver loaded prevent
system suspend?

there's also state such as features set which does need to be
preserved.

I think the thing to do is to skip invoking suspend/resume callback, and in
fact checking suspend/resume altogether.

> ---
>  drivers/vhost/vdpa.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index bc4a51e4638b..ce1882acfc3b 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -598,6 +598,9 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
>  	if (!ops->suspend)
>  		return -EOPNOTSUPP;
>  
> +	if (!(ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK))
> +		return -EINVAL;
> +
>  	ret = ops->suspend(vdpa);
>  	if (!ret)
>  		v->suspended = true;
> @@ -618,6 +621,9 @@ static long vhost_vdpa_resume(struct vhost_vdpa *v)
>  	if (!ops->resume)
>  		return -EOPNOTSUPP;
>  
> +	if (!(ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK))
> +		return -EINVAL;
> +
>  	ret = ops->resume(vdpa);
>  	if (!ret)
>  		v->suspended = false;
> -- 
> 2.39.3