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From: Mike Kravetz <mike.kravetz@oracle.com>
To: Muchun Song <songmuchun@bytedance.com>,
	akpm@linux-foundation.org, zi.yan@cs.rutgers.edu,
	kirill.shutemov@linux.intel.com, rientjes@google.com,
	lars.persson@axis.com, ziy@nvidia.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	duanxiongchun@bytedance.com, fam.zheng@bytedance.com
Subject: Re: [PATCH v4 4/5] mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte()
Date: Wed, 9 Feb 2022 10:59:20 -0800	[thread overview]
Message-ID: <cf985291-36a9-e60e-f1e1-f12719c7b3fb@oracle.com> (raw)
In-Reply-To: <20220208073617.70342-5-songmuchun@bytedance.com>

On 2/7/22 23:36, Muchun Song wrote:
> folio_copy() will copy the data from one page to the target page, then
> the target page will be mapped to the user space address, which might
> have an alias issue with the kernel address used to copy the data from
> the page to.  There are 2 ways to fix this issue.
> 
>  1) insert flush_dcache_page() after folio_copy().
>  2) replace folio_copy() with copy_user_huge_page() which already
>     considers the cache maintenance.
> 
> We chose 2) way to fix the issue since architectures can optimize this
> situation.
> 
> Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  mm/hugetlb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Thanks!  This will also make backports easier.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

-- 
Mike Kravetz


  reply	other threads:[~2022-02-09 18:59 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-08  7:36 [PATCH v4 0/5] Fix some cache flush bugs Muchun Song
2022-02-08  7:36 ` [PATCH v4 1/5] mm: thp: fix wrong cache flush in remove_migration_pmd() Muchun Song
2022-02-08  7:36 ` [PATCH v4 2/5] mm: fix missing cache flush for all tail pages of compound page Muchun Song
2022-02-08  7:36 ` [PATCH v4 3/5] mm: hugetlb: fix missing cache flush in copy_huge_page_from_user() Muchun Song
2022-02-09 19:07   ` Mike Kravetz
2022-02-10  7:19     ` Muchun Song
2022-02-08  7:36 ` [PATCH v4 4/5] mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte() Muchun Song
2022-02-09 18:59   ` Mike Kravetz [this message]
2022-02-08  7:36 ` [PATCH v4 5/5] mm: replace multiple dcache flush with flush_dcache_folio() Muchun Song
2022-02-09 19:10   ` Mike Kravetz

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