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Message-ID: <Y9AUsCxgitOI2lUA@x1n>
Date: Tue, 24 Jan 2023 12:26:08 -0500
From: Peter Xu <peterx@...hat.com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: David Hildenbrand <david@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Michał Mirosław <emmir@...gle.com>,
Andrei Vagin <avagin@...il.com>,
Danylo Mocherniuk <mdanylo@...gle.com>,
Paul Gofman <pgofman@...eweavers.com>,
Cyrill Gorcunov <gorcunov@...il.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Shuah Khan <shuah@...nel.org>,
Christian Brauner <brauner@...nel.org>,
Yang Shi <shy828301@...il.com>,
Vlastimil Babka <vbabka@...e.cz>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Yun Zhou <yun.zhou@...driver.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Alex Sierra <alex.sierra@....com>,
Matthew Wilcox <willy@...radead.org>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
"Gustavo A . R . Silva" <gustavoars@...nel.org>,
Dan Williams <dan.j.williams@...el.com>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
Greg KH <gregkh@...uxfoundation.org>, kernel@...labora.com
Subject: Re: [PATCH v7 1/4] userfaultfd: Add UFFD WP Async support
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
--
Peter Xu
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