RE: [RFC 2/3] vdpa: support exposing the count of vqs to userspace

[Longpeng (Mike, Cloud Infrastructure Service Product Dept.)]

Hi Jason,

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@xxxxxxxxxx]
> Sent: Tuesday, January 18, 2022 11:08 AM
> To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
> <longpeng2@xxxxxxxxxx>; mst@xxxxxxxxxx; sgarzare@xxxxxxxxxx;
> stefanha@xxxxxxxxxx
> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Gonglei (Arei)
> <arei.gonglei@xxxxxxxxxx>; Yechuan <yechuan@xxxxxxxxxx>; Huangzhichao
> <huangzhichao@xxxxxxxxxx>
> Subject: Re: [RFC 2/3] vdpa: support exposing the count of vqs to userspace
> 
> 
> 在 2022/1/17 下午5:29, Longpeng(Mike) 写道:
> > From: Longpeng <longpeng2@xxxxxxxxxx>
> >
> > - GET_VQS_COUNT: the count of virtqueues that exposed
> >
> > Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
> > ---
> >   drivers/vhost/vdpa.c       | 13 +++++++++++++
> >   include/uapi/linux/vhost.h |  3 +++
> >   2 files changed, 16 insertions(+)
> >
> > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > index 1eea14a4ea56..c1074278fc6b 100644
> > --- a/drivers/vhost/vdpa.c
> > +++ b/drivers/vhost/vdpa.c
> > @@ -369,6 +369,16 @@ static long vhost_vdpa_get_config_size(struct vhost_vdpa
> *v, u32 __user *argp)
> >   	return 0;
> >   }
> >
> > +static long vhost_vdpa_get_vqs_count(struct vhost_vdpa *v, u32 __user *argp)
> > +{
> > +	struct vdpa_device *vdpa = v->vdpa;
> 
> 
> While at it, I think it's better to change vdpa->nvqs to use u32?
> 

struct vhost_vdpa {
    ...
	int nvqs;
    ...
};

struct vdpa_device {
    ...
	int nvqs;
    ...
};

I think we should change both to u32?


> Thanks
> 
> 
> > +
> > +	if (copy_to_user(argp, &vdpa->nvqs, sizeof(vdpa->nvqs)))
> > +		return -EFAULT;
> > +
> > +	return 0;
> > +}
> > +
> >   static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> >   				   void __user *argp)
> >   {
> > @@ -509,6 +519,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> >   	case VHOST_VDPA_GET_CONFIG_SIZE:
> >   		r = vhost_vdpa_get_config_size(v, argp);
> >   		break;
> > +	case VHOST_VDPA_GET_VQS_COUNT:
> > +		r = vhost_vdpa_get_vqs_count(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 bc74e95a273a..5d99e7c242a2 100644
> > --- a/include/uapi/linux/vhost.h
> > +++ b/include/uapi/linux/vhost.h
> > @@ -154,4 +154,7 @@
> >   /* Get the config size */
> >   #define VHOST_VDPA_GET_CONFIG_SIZE	_IOR(VHOST_VIRTIO, 0x79, __u32)
> >
> > +/* Get the count of all virtqueues */
> > +#define VHOST_VDPA_GET_VQS_COUNT	_IOR(VHOST_VIRTIO, 0x80, __u32)
> > +
> >   #endif