Subject: Re: [PATCH V6 mlx5-next 07/15] vfio: Have the core code decode the VFIO_DEVICE_FEATURE ioctl

From: Jason Gunthorpe <[email-masked]>
Date: Mon, 31 Jan 2022 20:11:48 -0400

On Mon, Jan 31, 2022 at 04:41:43PM -0700, Alex Williamson wrote:
> > +int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags,
> > +				void __user *arg, size_t argsz)
> > +{
> > +	struct vfio_pci_core_device *vdev =
> > +		container_of(device, struct vfio_pci_core_device, vdev);
> > +	uuid_t uuid;
> > +	int ret;
> 
> Nit, should uuid at least be scoped within the token code?  Or token
> code pushed to a separate function?

Sure, it wasn't done before, but it would be nicer,.

> > +static inline int vfio_check_feature(u32 flags, size_t argsz, u32 supported_ops,
> > +				    size_t minsz)
> > +{
> > +	if ((flags & (VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_SET)) &
> > +	    ~supported_ops)
> > +		return -EINVAL;
> 
> These look like cases where it would be useful for userspace debugging
> to differentiate errnos.

I tried to keep it unchanged from what it was today.

> -EOPNOTSUPP?

This would be my preference, but it would also be the first use in
vfio

> > +	if (flags & VFIO_DEVICE_FEATURE_PROBE)
> > +		return 0;
> > +	/* Without PROBE one of GET or SET must be requested */
> > +	if (!(flags & (VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_SET)))
> > +		return -EINVAL;
> > +	if (argsz < minsz)
> > +		return -EINVAL;
>
> -ENOSPC?

Do you want to do all of these minsz then? There are lots..

Jason