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Fri, 22 May 2026 06:39:24 -0400 (EDT) Date: Fri, 22 May 2026 11:39:20 +0100 From: Kiryl Shutsemau To: Mike Rapoport Cc: akpm@linux-foundation.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, sj@kernel.org, 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 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 9orf6syk7zddg35rujyk84tk5yz8ggga X-Rspamd-Queue-Id: DD601140009 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1779446368-657596 X-HE-Meta: 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 wepNx6nU Qc887pOU8ElRdIrqh2Zkx16aV5mOo+mXf1NoN+63Mcu3DmIOvC305PGxxUH4oY9ZnWBuSry2A19pViPJCjrXeRg1+KmzRsGn69T4huWuAk+oOvudcWYIy7E9DmenBKQYWlxVQZJwt6EjAXvWJSLXxnHZr305eeWLjIatb8lakSz3BRqsqtkjGqCUm9ddgFO8P7if2OI718S+51BjNUIbl9mu2VDPfvqBykgGQoNgujVQ7WxMuuztjHkz5z/ZxmBwGndj3a94k10J3Ylfs3uO15KaDJsJRX3PtagBlyfZ13SP8V6+vkGv5291sTN/fWEFTQX+oEml1h9k8SDRqmErMmLyFhRiD8cQu8Ny2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 12, 2026 at 07:48:57PM +0300, Mike Rapoport wrote: > On Fri, May 08, 2026 at 04:55:16PM +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. > > And nothing check for it as well, am I right? Yep. > Worth noting here, IMHO. Will do. > > > Signed-off-by: Kiryl Shutsemau > > Assisted-by: Claude:claude-opus-4-6 > > --- > > 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/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > > index 98f546e83cd2..fcf308dba311 100644 > > --- a/include/linux/userfaultfd_k.h > > +++ b/include/linux/userfaultfd_k.h > > @@ -21,10 +21,11 @@ > > #include > > > > /* The set of all possible UFFD-related VM flags. */ > > -#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR) > > +#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR | \ > > + VM_UFFD_RWP) > > Nit: can we keep mode bits together and protection bits together here and > in the below changes? Yep, make sense. > Otherwise looks good to me > > Reviewed-by: Mike Rapoport (Microsoft) Thanks! -- Kiryl Shutsemau / Kirill A. Shutemov