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From: SJ Park <sj@kernel.org>
To: SJ Park <sj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	stable@vger.kernel.org,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	damon@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH] mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold()
Date: Mon,  7 Sep 2026 11:08:20 -0700
Message-ID: <20260907180821.102875-1-sj@kernel.org>
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On Mon,  7 Sep 2026 10:03:56 -0700 SJ Park <sj@kernel.org> wrote:

[...]
> +static bool damon_hugetlb_ptep_mkold(pte_t *pte, struct mm_struct *mm,
> +		struct vm_area_struct *vma, unsigned long addr, pte_t *entry)
> +{
> +	unsigned long psize = huge_page_size(hstate_vma(vma));
> +
> +	if (!pte_young(*entry))
> +		return false;
> +	*entry = huge_ptep_get_and_clear(mm, addr, pte, psize);
> +	*entry = pte_mkold(*entry);
> +	set_huge_pte_at(mm, addr, pte, *entry, psize);
> +	return true;

Sashiko says [1] this might violate BBM.  But this is only for accessed bit
change.  So I don't think BBM is required here.  Also, we intentionally do not
flush TLB because this is just a best-effort monitoring.  Please correct me if
I'm wrong.

[1] https://lore.kernel.org/20260907171613.A09B11F00A3A@smtp.kernel.org


Thanks,
SJ

[...]