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

On Mon, Jul 12, 2021 at 06:41:21PM +0000, Michael Kelley wrote:

From: Wei Liu <wei.liu@kernel.org> Sent: Monday, July 12, 2021 11:24 AM

quoted

On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
[...]

quoted

+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.

OK. That's good.

Wei.

Michael