From: Peter Xu <peterx@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Jerome Glisse <jglisse@redhat.com>, Shaohua Li <shli@fb.com>
Subject: Re: [PATCH v1] mm/userfaultfd: propagate uffd-wp bit when PTE-mapping the huge zeropage
Date: Thu, 2 Mar 2023 17:29:50 -0500 [thread overview]
Message-ID: <ZAEjXqNH+U8p9fOG@x1n> (raw)
In-Reply-To: <20230302175423.589164-1-david@redhat.com>
On Thu, Mar 02, 2023 at 06:54:23PM +0100, David Hildenbrand wrote:
> Currently, we'd lose the userfaultfd-wp marker when PTE-mapping a huge
> zeropage, resulting in the next write faults in the PMD range
> not triggering uffd-wp events.
>
> Various actions (partial MADV_DONTNEED, partial mremap, partial munmap,
> partial mprotect) could trigger this. However, most importantly,
> un-protecting a single sub-page from the userfaultfd-wp handler when
> processing a uffd-wp event will PTE-map the shared huge zeropage and
> lose the uffd-wp bit for the remainder of the PMD.
>
> Let's properly propagate the uffd-wp bit to the PMDs.
Ouch.. I thought this was reported once, probably it fell through the
cracks.
Acked-by: Peter Xu <peterx@redhat.com>
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2023-03-02 22:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-02 17:54 David Hildenbrand
2023-03-02 22:29 ` Peter Xu [this message]
2023-03-03 9:12 ` David Hildenbrand
2023-03-03 14:32 ` Peter Xu
2023-03-03 1:57 ` Andrew Morton
2023-03-03 9:12 ` David Hildenbrand
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