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

Steffen Eiden
2022-05-13T12:35:24Z

On 5/13/22 10:37, Claudio Imbrenda wrote:
> 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?
>
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]