On Wed, Nov 02, 2022 at 11:44:51AM -0700, Elliot Berman wrote:
>
>
> On 11/2/2022 12:31 AM, Arnd Bergmann wrote:
> > On Wed, Oct 26, 2022, at 20:58, Elliot Berman wrote:
> >
> > > +static const struct file_operations gh_vm_fops = {
> > > + .unlocked_ioctl = gh_vm_ioctl,
> > > + .release = gh_vm_release,
> > > + .llseek = noop_llseek,
> > > +};
> >
> > There should be a .compat_ioctl entry here, otherwise it is
> > impossible to use from 32-bit tasks. If all commands have
> > arguments passed through a pointer to a properly defined
> > structure, you can just set it to compat_ptr_ioctl.
> >
>
> Ack.
>
> > > +static long gh_dev_ioctl_create_vm(unsigned long arg)
> > > +{
> > > + struct gunyah_vm *ghvm;
> > > + struct file *file;
> > > + int fd, err;
> > > +
> > > + /* arg reserved for future use. */
> > > + if (arg)
> > > + return -EINVAL;
> >
> > Do you have something specific in mind here? If 'create'
> > is the only command you support, and it has no arguments,
> > it would be easier to do it implicitly during open() and
> > have each fd opened from /dev/gunyah represent a new VM.
> >
>
> I'd like the argument here to support different types of virtual machines. I
> want to leave open what "different types" can be in case something new comes
> up in the future, but immediately "different type" would correspond to a few
> different authentication mechanisms for virtual machines that Gunyah
> supports.
Please don't add code that does not actually do something now, as that
makes it impossible to review properly, _AND_ no one knows what is going
to happen in the future. In the future, you can just add a new ioctl
and all is good, no need to break working userspace by suddenly looking
at the arg value and doing something with it.
thanks,
greg k-h
