RE: [PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Michael Kelley <mikelley@microsoft.com>]

From: Wei Liu <wei.liu@kernel.org> Sent: Monday, July 12, 2021 11:24 AM
> 
> On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
> [...]
> > +int hv_common_cpu_init(unsigned int cpu)
> > +{
> > +	void **inputarg, **outputarg;
> > +	u64 msr_vp_index;
> > +	gfp_t flags;
> > +	int pgcount = hv_root_partition ? 2 : 1;
> > +
> > +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > +	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> > +
> > +	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
> 
> This is changed from alloc_pages to kmalloc. Does it ensure the
> alignment is still correct?
> 
> Wei.

It does.  The alignment guarantee made by kmalloc() was changed a
couple of years ago.  See commit 59bb47985c1d.  Here's the current text
from the comments preceding kmalloc():

* The allocated object address is aligned to at least ARCH_KMALLOC_MINALIGN
 * bytes. For @size of power of two bytes, the alignment is also guaranteed
 * to be at least to the size.

Michael