2020-12-29 12:27:48

by Eli Cohen

Subject: Re: [PATCH 12/21] vhost-vdpa: introduce uAPI to get the number of virtqueue groups

On Wed, Dec 16, 2020 at 02:48:09PM +0800, Jason Wang wrote:
> Follows the vDPA support for multiple address spaces, this patch
> introduce uAPI for the userspace to know the number of virtqueue
> groups supported by the vDPA device.

Can you explain what exactly you mean be userspace? Is it just qemu or
is it destined to the virtio_net driver run by the qemu process?
Also can you say for what purpose?

>
> Signed-off-by: Jason Wang <[email protected]>
> ---
> drivers/vhost/vdpa.c | 4 ++++
> include/uapi/linux/vhost.h | 3 +++
> 2 files changed, 7 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 060d5b5b7e64..1ba5901b28e7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -536,6 +536,10 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> case VHOST_VDPA_GET_VRING_NUM:
> r = vhost_vdpa_get_vring_num(v, argp);
> break;
> + case VHOST_VDPA_GET_GROUP_NUM:
> + r = copy_to_user(argp, &v->vdpa->ngroups,
> + sizeof(v->vdpa->ngroups));
> + break;
> case VHOST_SET_LOG_BASE:
> case VHOST_SET_LOG_FD:
> r = -ENOIOCTLCMD;
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 59c6c0fbaba1..8a4e6e426bbf 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -145,4 +145,7 @@
> /* Get the valid iova range */
> #define VHOST_VDPA_GET_IOVA_RANGE _IOR(VHOST_VIRTIO, 0x78, \
> struct vhost_vdpa_iova_range)
> +/* Get the number of virtqueue groups. */
> +#define VHOST_VDPA_GET_GROUP_NUM _IOR(VHOST_VIRTIO, 0x79, unsigned int)
> +
> #endif
> --
> 2.25.1
>

2020-12-30 06:52:19

by Jason Wang

Subject: Re: [PATCH 12/21] vhost-vdpa: introduce uAPI to get the number of virtqueue groups

On 2020/12/29 下午8:24, Eli Cohen wrote:
> On Wed, Dec 16, 2020 at 02:48:09PM +0800, Jason Wang wrote:
>> Follows the vDPA support for multiple address spaces, this patch
>> introduce uAPI for the userspace to know the number of virtqueue
>> groups supported by the vDPA device.
> Can you explain what exactly you mean be userspace?


It's the userspace that uses the uAPI introduced in this patch.


> Is it just qemu or
> is it destined to the virtio_net driver run by the qemu process?


It could be Qemu, DPDK or other userspace program.

The guest virtio-net driver will not use this but talks to the virtio
device emulated by Qemu.


> Also can you say for what purpose?


This can be used for facilitate the checking of whether the control vq
could be supported.

E.g if the device support less than 2 groups, qemu won't advertise
control vq.

Yes, #groups could be inferred from GET_VRING_GROUP. But it's not
straightforward as this.

Thanks


>
>> Signed-off-by: Jason Wang <[email protected]>
>> ---
>> drivers/vhost/vdpa.c | 4 ++++
>> include/uapi/linux/vhost.h | 3 +++
>> 2 files changed, 7 insertions(+)
>>
>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>> index 060d5b5b7e64..1ba5901b28e7 100644
>> --- a/drivers/vhost/vdpa.c
>> +++ b/drivers/vhost/vdpa.c
>> @@ -536,6 +536,10 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>> case VHOST_VDPA_GET_VRING_NUM:
>> r = vhost_vdpa_get_vring_num(v, argp);
>> break;
>> + case VHOST_VDPA_GET_GROUP_NUM:
>> + r = copy_to_user(argp, &v->vdpa->ngroups,
>> + sizeof(v->vdpa->ngroups));
>> + break;
>> case VHOST_SET_LOG_BASE:
>> case VHOST_SET_LOG_FD:
>> r = -ENOIOCTLCMD;
>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>> index 59c6c0fbaba1..8a4e6e426bbf 100644
>> --- a/include/uapi/linux/vhost.h
>> +++ b/include/uapi/linux/vhost.h
>> @@ -145,4 +145,7 @@
>> /* Get the valid iova range */
>> #define VHOST_VDPA_GET_IOVA_RANGE _IOR(VHOST_VIRTIO, 0x78, \
>> struct vhost_vdpa_iova_range)
>> +/* Get the number of virtqueue groups. */
>> +#define VHOST_VDPA_GET_GROUP_NUM _IOR(VHOST_VIRTIO, 0x79, unsigned int)
>> +
>> #endif
>> --
>> 2.25.1
>>