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

Claudio Imbrenda
2022-05-13T08:38:16Z

On Fri, 13 May 2022 09:45:39 +0200
Steffen Eiden <seiden@linux.ibm.com> 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?

>
> [snip]
>