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SubjectRe: [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds()

On 4/24/2022 3:45 PM, Muchun Song wrote:
> On Sun, Apr 24, 2022 at 02:33:19PM +0800, Baolin Wang wrote:
>> Missed calling flush_cache_range() before removing the sharing PMD entrires,
>> otherwise data consistence issue may be occurred on some architectures whose
>> caches are strict and require a virtual–>physical translation to exist for
>> a virtual address. Thus add it.
>> Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
>> Signed-off-by: Baolin Wang <>
> CONFIG_ARCH_WANT_HUGE_PMD_SHARE is only definded on riscv, arm64 and
> x86. All of them do not have a VIVT cache. In others words,
> flush_cache_range() is null on those architectures. So I suspect
> in practice this does not cause any issue. It is better to
> clarify this in commit log.

Yes, just from code inspection and to keep same behaviors when unmapping
sharing PMD entrires in case more architectures can support
CONFIG_ARCH_WANT_HUGE_PMD_SHARE in future. Will update the commit
message in next version.

> Anyway:
> Reviewed-by: Muchun Song <>


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