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Date:   Thu, 6 Aug 2020 01:55:46 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, rob.miller@broadcom.com,
        lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com,
        shahafs@mellanox.com, hanand@xilinx.com, mhabets@solarflare.com,
        gdawar@xilinx.com, saugatm@xilinx.com, vmireyno@marvell.com,
        zhangweining@ruijie.com.cn, eli@mellanox.com
Subject: Re: [PATCH 4/4] vhost: vdpa: report iova range
Message-ID: <20200806015513-mutt-send-email-mst@kernel.org>
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On Thu, Aug 06, 2020 at 11:29:16AM +0800, Jason Wang wrote:
> 
> On 2020/8/5 下午8:58, Michael S. Tsirkin wrote:
> > 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@redhat.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?
> 
> 
> Because set_map || dma_ops is a hint that the device has its own DMA
> translation logic.
> 
> Device without get_iova_range does not necessarily meant it use IOMMU
> driver.
> 
> Thanks

OK let's add some code comments please, and check get_iova_range
is actually there before calling.

> 
> > 
> > 
> > 
> > 
> > > +		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