linux-kernel - Re: [RFC PATCH 03/26] hugetlb: add make_huge_pte_with

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Message-ID: <4889b697-c962-a043-f2d2-0788a5bd1deb@nutanix.com>
Date:   Mon, 27 Jun 2022 17:43:38 +0530
From:   "manish.mishra" <manish.mishra@...anix.com>
To:     James Houghton <jthoughton@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>
Cc:     David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Jue Wang <juew@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 03/26] hugetlb: add make_huge_pte_with_shift


On 24/06/22 11:06 pm, James Houghton wrote:
> This allows us to make huge PTEs at shifts other than the hstate shift,
> which will be necessary for high-granularity mappings.
>
> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>   mm/hugetlb.c | 33 ++++++++++++++++++++-------------
>   1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 5df838d86f32..0eec34edf3b2 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4686,23 +4686,30 @@ const struct vm_operations_struct hugetlb_vm_ops = {
>   	.pagesize = hugetlb_vm_op_pagesize,
>   };
reviewed-by: manish.mishra@...anix.com
>   
> +static pte_t make_huge_pte_with_shift(struct vm_area_struct *vma,
> +				      struct page *page, int writable,
> +				      int shift)
> +{
> +	bool huge = shift > PAGE_SHIFT;
> +	pte_t entry = huge ? mk_huge_pte(page, vma->vm_page_prot)
> +			   : mk_pte(page, vma->vm_page_prot);
> +
> +	if (writable)
> +		entry = huge ? huge_pte_mkwrite(entry) : pte_mkwrite(entry);
> +	else
> +		entry = huge ? huge_pte_wrprotect(entry) : pte_wrprotect(entry);
> +	pte_mkyoung(entry);
> +	if (huge)
> +		entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
> +	return entry;
> +}
> +
>   static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
> -				int writable)
> +			   int writable)
>   {
> -	pte_t entry;
>   	unsigned int shift = huge_page_shift(hstate_vma(vma));
>   
> -	if (writable) {
> -		entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
> -					 vma->vm_page_prot)));
> -	} else {
> -		entry = huge_pte_wrprotect(mk_huge_pte(page,
> -					   vma->vm_page_prot));
> -	}
> -	entry = pte_mkyoung(entry);
> -	entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
> -
> -	return entry;
> +	return make_huge_pte_with_shift(vma, page, writable, shift);
>   }
>   
>   static void set_huge_ptep_writable(struct vm_area_struct *vma,