Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device

[Steffen Eiden]

On 5/13/22 10:37, Claudio Imbrenda wrote:
> On Fri, 13 May 2022 09:45:39 +0200
> Steffen Eiden <seiden@xxxxxxxxxxxxx> wrote:
>
> > On 5/12/22 16:33, Claudio Imbrenda wrote:
> >
> > [snip]
> >
> > > > +/*
> > > > + * IOCTL entry point for the Ultravisor device.
> > > > + */
> > > > +static long uvio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> > > > +{
> > > > +	void __user *argp = (void __user *)arg;
> > > > +	struct uvio_ioctl_cb *uv_ioctl;
> > > > +	long ret;
> > > > +
> > > > +	ret = -ENOMEM;
> > > > +	uv_ioctl = vzalloc(sizeof(*uv_ioctl));
> > > struct uvio_ioctl_cb is rather small, couldn't you just allocate it on
> > > the stack?
> > >    
> > IIRC it was on stack in some previous version. We then had a discussion
> > earlier about this triggered by the inverse comment and decided to not
> > use the stack.
>
> ok fair enough
>
> but what's the reason for a vzalloc instead of a kzalloc, when the
> allocation is surely going to be small?
We had no strong reasons against or for vzalloc/kzalloc.
If you want me to change it to kzalloc I can do it. I still
have no strong opinion on that.

> > [snip]