linux-kernel - [PATCH v1 0/2] mm/hugetlb: uffd-wp fixes for hugetlb_change

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Message-Id: <20221222205511.675832-1-david@redhat.com>
Date:   Thu, 22 Dec 2022 21:55:09 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Peter Xu <peterx@...hat.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Miaohe Lin <linmiaohe@...wei.com>
Subject: [PATCH v1 0/2] mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()

Playing with virtio-mem and background snapshots (using uffd-wp) on
hugetlb in QEMU, I managed to trigger a VM_BUG_ON(). Looking into the
details, hugetlb_change_protection() seems to not handle uffd-wp correctly
in all cases.

Patch #1 fixes my test case. I don't have reproducers for patch #2, as
it requires running into migration entries.

I did not yet check in detail yet if !hugetlb code requires similar care.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Muchun Song <muchun.song@...ux.dev>
Cc: Miaohe Lin <linmiaohe@...wei.com>

David Hildenbrand (2):
  mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
  mm/hugetlb: fix uffd-wp handling for migration entries in
    hugetlb_change_protection()

 mm/hugetlb.c | 38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

-- 
2.38.1