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

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Message-ID: <Y6TJYl78od9XQuvj@x1n>
Date:   Thu, 22 Dec 2022 16:17:22 -0500
From:   Peter Xu <peterx@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Miaohe Lin <linmiaohe@...wei.com>
Subject: Re: [PATCH v1 0/2] mm/hugetlb: uffd-wp fixes for
 hugetlb_change_protection()

On Thu, Dec 22, 2022 at 09:55:09PM +0100, David Hildenbrand wrote:
> 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()

Reviewed-by: Peter Xu <peterx@...hat.com>

Thanks, David.

-- 
Peter Xu