linux-kernel - Re: [PATCH 4/4] vhost: vdpa: report iova range

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Date:   Wed, 5 Aug 2020 08:58:02 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, rob.miller@...adcom.com,
        lingshan.zhu@...el.com, eperezma@...hat.com, lulu@...hat.com,
        shahafs@...lanox.com, hanand@...inx.com, mhabets@...arflare.com,
        gdawar@...inx.com, saugatm@...inx.com, vmireyno@...vell.com,
        zhangweining@...jie.com.cn, eli@...lanox.com
Subject: Re: [PATCH 4/4] vhost: vdpa: report iova range

On Wed, Jun 17, 2020 at 11:29:47AM +0800, Jason Wang wrote:
> This patch introduces a new ioctl for vhost-vdpa device that can
> report the iova range by the device. For device that depends on
> platform IOMMU, we fetch the iova range via DOMAIN_ATTR_GEOMETRY. For
> devices that has its own DMA translation unit, we fetch it directly
> from vDPA bus operation.
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/vhost/vdpa.c             | 27 +++++++++++++++++++++++++++
>  include/uapi/linux/vhost.h       |  4 ++++
>  include/uapi/linux/vhost_types.h |  5 +++++
>  3 files changed, 36 insertions(+)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 77a0c9fb6cc3..ad23e66cbf57 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -332,6 +332,30 @@ static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)
>  
>  	return 0;
>  }
> +
> +static long vhost_vdpa_get_iova_range(struct vhost_vdpa *v, u32 __user *argp)
> +{
> +	struct iommu_domain_geometry geo;
> +	struct vdpa_device *vdpa = v->vdpa;
> +	const struct vdpa_config_ops *ops = vdpa->config;
> +	struct vhost_vdpa_iova_range range;
> +	struct vdpa_iova_range vdpa_range;
> +
> +	if (!ops->set_map && !ops->dma_map) {

Why not just check if (ops->get_iova_range) directly?




> +		iommu_domain_get_attr(v->domain,
> +				      DOMAIN_ATTR_GEOMETRY, &geo);
> +		range.start = geo.aperture_start;
> +		range.end = geo.aperture_end;
> +	} else {
> +		vdpa_range = ops->get_iova_range(vdpa);
> +		range.start = vdpa_range.start;
> +		range.end = vdpa_range.end;
> +	}
> +
> +	return copy_to_user(argp, &range, sizeof(range));
> +
> +}
> +
>  static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>  				   void __user *argp)
>  {
> @@ -442,6 +466,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>  	case VHOST_VDPA_SET_CONFIG_CALL:
>  		r = vhost_vdpa_set_config_call(v, argp);
>  		break;
> +	case VHOST_VDPA_GET_IOVA_RANGE:
> +		r = vhost_vdpa_get_iova_range(v, argp);
> +		break;
>  	default:
>  		r = vhost_dev_ioctl(&v->vdev, cmd, argp);
>  		if (r == -ENOIOCTLCMD)
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 0c2349612e77..850956980e27 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -144,4 +144,8 @@
>  
>  /* Set event fd for config interrupt*/
>  #define VHOST_VDPA_SET_CONFIG_CALL	_IOW(VHOST_VIRTIO, 0x77, int)
> +
> +/* Get the valid iova range */
> +#define VHOST_VDPA_GET_IOVA_RANGE	_IOW(VHOST_VIRTIO, 0x78, \
> +					     struct vhost_vdpa_iova_range)
>  #endif
> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> index 669457ce5c48..4025b5a36177 100644
> --- a/include/uapi/linux/vhost_types.h
> +++ b/include/uapi/linux/vhost_types.h
> @@ -127,6 +127,11 @@ struct vhost_vdpa_config {
>  	__u8 buf[0];
>  };
>  
> +struct vhost_vdpa_iova_range {
> +	__u64 start;
> +	__u64 end;
> +};
> +


Pls document fields. And I think first/last is a better API ...

>  /* Feature bits */
>  /* Log all write descriptors. Can be changed while device is active. */
>  #define VHOST_F_LOG_ALL 26
> -- 
> 2.20.1