Re: [PATCH] powerpc/npu: Cleanup MMIO ATSD flushing

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Balbir Singh <bsingharora@gmail.com> writes:

 +	address = start;
> +	do {
> +		local_irq_disable();
> +		find_linux_pte(mm->pgd, address, &is_thp, &hshift);
> +		if (!is_thp)
> +			shift = PAGE_SHIFT;

It can still be hugetlb if is_thp is false.

> +		else if (hshift && !is_thp)
> +			shift = hshift;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +		else
> +			shift = HPAGE_PMD_SIZE;

That is wrong. I guess it should be shift = HPAGE_PMD_SHIFT. But i am
not sure we need to make it this complex at all. See below.

> +#else
> +		else {
> +			shift = PAGE_SHIFT;
> +			pr_warn_once("unsupport page size for mm %p,addr %lx\n",
> +					mm, start);
> +		}
> +#endif

I am still not sure this is correct from a pure page table walking
point. Why not

       if (hshift)
          shift = hshift;
       else
          shift = PAGE_SHIFT;

if you didn't want to differentiate between thp and hugetlb mapping you
can drop is_thp completely.

-aneesh