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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Thu, 10 Feb 2022 15:19:57 +0800
Message-ID: <CAMZfGtUTj-r-sO3YRfyEhvR1mKYxi6kXx+ZZPVYjV3AhAMdh1g@mail.gmail.com>
Subject: Re: [PATCH v4 3/5] mm: hugetlb: fix missing cache flush in copy_huge_page_from_user()
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>, zi.yan@cs.rutgers.edu,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Lars Persson <lars.persson@axis.com>, Zi Yan <ziy@nvidia.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        Fam Zheng <fam.zheng@bytedance.com>
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On Thu, Feb 10, 2022 at 3:07 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 2/7/22 23:36, Muchun Song wrote:
> > The userfaultfd calls copy_huge_page_from_user() which does not do
> > any cache flushing for the target page.  Then the target page will
> > be mapped to the user space with a different address (user address),
> > which might have an alias issue with the kernel address used to copy
> > the data from the user to.  Fix this issue by flushing dcache in
> > copy_huge_page_from_user().
>
> Quick question.
>
> Should this also be done for the non-hugetlb case?  Take a look at the
> routines __mcopy_atomic() and mcopy_atomic_pte().  Or, is that somehow
> handled?

Actually, you are right. __mcopy_atomic() and mcopy_atomic_pte()
should also be fixed.  And shmem_mfill_atomic_pte() also should
be fixed. I'll fix those places in the next version. Thanks.

>
> For this change,
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

Thanks Mike.