# RE: \[PATCH v8 1/6\] arm64: hyperv: Add Hyper-V hypercall and register access utilities

- From: Sunil Muthuswamy \<hidden\>
- Date: 2021-03-03 20:58:19 
- List: linux-hyperv
- Page: https://ratatoskr.run/linux-hyperv/2021/03/6287255
- Thread: https://ratatoskr.run/linux-arm-kernel/2021/03/6286192/t.md

```text
> > +
> > +	/*
> > +	 * Allocate a power of 2 size so alignment to that size is
> > +	 * guaranteed, since the hypercall input and output areas
> > +	 * must not cross a page boundary.
> > +	 */
> > +	input = kzalloc(roundup_pow_of_two(sizeof(input->header) +
> > +				sizeof(input->element[0])), GFP_ATOMIC);
> > +	output = kmalloc(roundup_pow_of_two(sizeof(*output)), GFP_ATOMIC);
> > +
> Check for null from these malloc routines? Here and in other places.

Between, is there a plan to setup a percpu input/output page for hypercall
input/output on ARM (like we do for x64)? I didn't check the specific size requirement
for this particular call, but, that generally will remove the need for these
allocations.
```