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b=MVYp41fAvhbcH6lzP0iL6HNSyElsHkR/Q+lCcK30GKR9H+vj/MFLMhVAd1v3csNBH kCRRLysqV5YMJFMOV6lswhv3RvvBpMfR2bkseMs7x1fgO80AOzV7wFLKTSA3jxdTG7 4zuPMR9SAUtFtCXPf5J6eezX1IAiSYrGOKubXJhq23H6MzYOcCZNlpFyZEyFR9HoKP SAFAOfpvqHOAVV5BcpOkfaMeaiZGEvbuoDtViEk8oIkwPs+H3BHTg7rUVyKBjchDro vUntATzUUqvhc7aImuP5dFv32fo4BeHGidQoMpsgDOJmfeL1HQEENTFp7xigaOgRd5 16CGzJTwhE2yg== From: SeongJae Park To: "Kiryl Shutsemau (Meta)" Cc: SeongJae Park , akpm@linux-foundation.org, rppt@kernel.org, peterx@redhat.com, david@kernel.org, ljs@kernel.org, surenb@google.com, vbabka@kernel.org, Liam.Howlett@oracle.com, ziy@nvidia.com, corbet@lwn.net, skhan@linuxfoundation.org, seanjc@google.com, pbonzini@redhat.com, jthoughton@google.com, aarcange@redhat.com, usama.arif@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2 04/14] mm: add VM_UFFD_RWP VMA flag Date: Thu, 14 May 2026 17:29:31 -0700 Message-ID: <20260515002932.124892-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 5661C14000F X-Rspam-User: X-Stat-Signature: 6abroqr6xkmgdmgwuqxj7hsr4oijr57a X-HE-Tag: 1778804987-397770 X-HE-Meta: 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 pabCt7BX x1N3BIbbZoj3kXMqWBxLSg644t/xgUVLTOejALsmOsHiZjtYLZ6jho4QEgRPSGmRSm47Dk0aKqPyFeb0oboLWMLN1L9I3l48d+3x3XTbxuGoxThAm4i+uU7Cdz8E1/ZW1RKmoeICIEZj7REXSQbnmVirmjUCYUGg6vw4lW/4fE+BFpswWFal8d1bU8wU+TDQ3pCLslgGrqeivZh+Zvb9qALRKJ7di2XIMajQvMJ9RH66ay6xY1TRAtcXDm4GqBx3kLzYq7bqvdL9M+9DJ8TxxPyqN0w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 8 May 2026 16:55:16 +0100 "Kiryl Shutsemau (Meta)" wrote: > Preparatory patch for userfaultfd read-write protection (RWP). RWP > extends userfaultfd protection from plain write-protection (WP) to > full read-write protection: accesses to an RWP-protected range -- > reads as well as writes -- trap through userfaultfd. > > RWP marks ranges by combining PAGE_NONE with the uffd PTE bit, so > the flag is only meaningful when both primitives exist. A new > CONFIG_USERFAULTFD_RWP Kconfig symbol auto-selects when CONFIG_64BIT, > CONFIG_ARCH_HAS_PTE_PROTNONE, and CONFIG_HAVE_ARCH_USERFAULTFD_WP > are all set; call sites that gate on the flag depend on the symbol. > Elsewhere VM_UFFD_RWP aliases VM_NONE and every downstream check > folds to dead code. > > Nothing sets the flag yet. > > Signed-off-by: Kiryl Shutsemau > Assisted-by: Claude:claude-opus-4-6 A silly but loud thought. Would it make more sense to put Signed-off-by: after Assisted-by: ? > --- > Documentation/filesystems/proc.rst | 1 + > fs/proc/task_mmu.c | 3 +++ > include/linux/mm.h | 28 +++++++++++++++++---------- > include/linux/userfaultfd_k.h | 31 +++++++++++++++++++++++++----- > include/trace/events/mmflags.h | 7 +++++++ > mm/Kconfig | 9 +++++++++ > 6 files changed, 64 insertions(+), 15 deletions(-) > > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst > index db6167befb7b..db28207c5290 100644 > --- a/Documentation/filesystems/proc.rst > +++ b/Documentation/filesystems/proc.rst > @@ -607,6 +607,7 @@ encoded manner. The codes are the following: > um userfaultfd missing tracking > uw userfaultfd wr-protect tracking > ui userfaultfd minor fault > + ur userfaultfd read-write-protect tracking Yet another silly but loud thought. My first feeling on this was that this reads like 'u'serfaultfd 'r'ead-protect. And was further thinking 'uf' for just 'u'seffaultfd 'f'ault or 'up' for 'u'serfault-'p'rotect might make sense. But ended up thinking this is too trivial and ain't really matter. [...] > diff --git a/mm/Kconfig b/mm/Kconfig > index e8bf1e9e6ad9..ccf534a8cbc9 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1347,6 +1347,15 @@ config HAVE_ARCH_USERFAULTFD_MINOR > help > Arch has userfaultfd minor fault support > > +config USERFAULTFD_RWP > + def_bool y > + depends on 64BIT && ARCH_HAS_PTE_PROTNONE && HAVE_ARCH_USERFAULTFD_WP > + help > + Userfaultfd read-write protection (UFFDIO_RWPROTECT) delivers a Seems UFFDIO_RWPROTECT will be introduced later. Would it make more sense to add this config together with the patch? > + userfaultfd notification on every access -- read or write -- to a > + protected range, letting userspace observe the working set of a > + process. > + > menuconfig USERFAULTFD > bool "Enable userfaultfd() system call" > depends on MMU > -- > 2.51.2 > > None of my comments is a blocker. Reviewed-by: SeongJae Park Thanks, SJ