Re: [RFC PATCH 09/26] hugetlb: add hugetlb_hgm_enabled

["manish.mishra" <manish.mishra@nutanix.com>]

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reviewed-by: manish.mishra@nutanix.com

On 24/06/22 11:06 pm, James Houghton wrote:
> Currently, this is always true if the VMA is shared. In the future, it's
> possible that private mappings will get some or all HGM functionality.
>
> Signed-off-by: James Houghton<jthoughton@google.com>
> ---
>   include/linux/hugetlb.h | 10 ++++++++++
>   mm/hugetlb.c            |  8 ++++++++
>   2 files changed, 18 insertions(+)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 33ba48fac551..e7a6b944d0cc 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -1174,6 +1174,16 @@ static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
>   }
>   #endif	/* CONFIG_HUGETLB_PAGE */
>   
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +/* If HugeTLB high-granularity mappings are enabled for this VMA. */
> +bool hugetlb_hgm_enabled(struct vm_area_struct *vma);
> +#else
> +static inline bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
> +{
> +	return false;
> +}
> +#endif
> +
>   static inline spinlock_t *huge_pte_lock(struct hstate *h,
>   					struct mm_struct *mm, pte_t *pte)
>   {
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index a2d2ffa76173..8b10b941458d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6983,6 +6983,14 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
>   
>   #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
>   
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
> +{
> +	/* All shared VMAs have HGM enabled. */
> +	return vma->vm_flags & VM_SHARED;
> +}
> +#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
> +
>   /*
>    * These functions are overwritable if your architecture needs its own
>    * behavior.

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