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Subject: Re: [PATCH 4/4] vhost: vdpa: report iova range
To:     "Michael S. Tsirkin" <mst@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
References: <20200617032947.6371-1-jasowang@redhat.com>
 <20200617032947.6371-5-jasowang@redhat.com>
 <20200805085635-mutt-send-email-mst@kernel.org>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <357f681b-fdee-cc04-3cf3-04035c555893@redhat.com>
Date:   Thu, 6 Aug 2020 11:29:16 +0800
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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


>
>
>
>
>> +		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