linux-kernel - Re: [PATCH v2 1/3] mm: hugetlb: Considering PMD sharing when flushing cache/TLBs

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Date:   Thu, 28 Apr 2022 10:55:59 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        almasrymina@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] mm: hugetlb: Considering PMD sharing when
 flushing cache/TLBs

On Wed, Apr 27, 2022 at 06:52:05PM +0800, Baolin Wang wrote:
> When moving hugetlb page tables, the cache flushing is called in
> move_page_tables() without considering the shared PMDs, which may
> be cause cache issues on some architectures.
> 
> Thus we should move the hugetlb cache flushing into
> move_hugetlb_page_tables() with considering the shared PMDs ranges,
> calculated by adjust_range_if_pmd_sharing_possible(). Meanwhile also
> expanding the TLBs flushing range in case of shared PMDs.
> 
> Note this is discovered via code inspection, and did not meet a real
> problem in practice so far.
> 
> Fixes: 550a7d60bd5e ("mm, hugepages: add mremap() support for hugepage backed vma")
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

LGTM.

Reviewed-by: Muchun Song <songmuchun@...edance.com>

Thanks.