Message-ID: <1310badc-5fcd-dc98-9b5c-85044c6c7083@collabora.com>
Date:   Wed, 25 Jan 2023 17:18:52 +0500
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Cc:     Muhammad Usama Anjum <usama.anjum@collabora.com>,
        David Hildenbrand <david@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Cyrill Gorcunov <gorcunov@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
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        Christian Brauner <brauner@kernel.org>,
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        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        Greg KH <gregkh@linuxfoundation.org>, kernel@collabora.com
Subject: Re: [PATCH v7 1/4] userfaultfd: Add UFFD WP Async support
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To:     Peter Xu <peterx@redhat.com>
References: <20230109064519.3555250-1-usama.anjum@collabora.com>
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 <Y9AUsCxgitOI2lUA@x1n>
From:   Muhammad Usama Anjum <usama.anjum@collabora.com>
In-Reply-To: <Y9AUsCxgitOI2lUA@x1n>
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On 1/24/23 10:26 PM, Peter Xu wrote:
> On Mon, Jan 23, 2023 at 03:11:20PM +0500, Muhammad Usama Anjum wrote:
>>> One thing worth mention is, I think for async wp it doesn't need to be
>>> restricted by UFFD_USER_MODE_ONLY, because comparing to the sync messages
>>> it has no risk of being utilized for malicious purposes.
>> I think with updated handling path updated in do_wp_page() and
>> wp_huge_pmd() in version, UFFD_USER_MODE_ONLY will not affect us.
> 
> This is more or less a comment for the design, the new code should work (by
> bypassing handle_userfaultfd(), where this bit was checked).
> 
> We'll need an man page update if this feature will be merged [1], and if so
> it'll need to be updated for the UFFD_USER_MODE_ONLY section regarding to
> async uffd-wp support too.  I think that can also be worked out after the
> series being accepted first, so just a heads up.
> 
> [1] https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
Thank you for explaining it. Definitely, we'll update the man pages after
the change has been merged. I've added it to my notes.>

-- 
BR,
Muhammad Usama Anjum