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b=b2v/Ws4X/OrJeoVd2MADb1/OzwlF6mfWpHskl0n53AtfrSWsGgexN3Yaa2xwr+Tgb NxYvlMdRrDNzJNcemlWPWIZafZlAJ+IbO2Ay2XBX5cKlRzDab8WGSMMtKIdylDbLPH joRzNAZdmyWyHGAzrW5zkWygvSxFheziGrqE4vs0cldK2Jz7LgE7peYrq7dPzjGpsZ MdFNSGR6VDJSvQ1tnOQNvcAgH6LWWf8fCUvCYtWzKfh4MpqTCf0r8FubYVyZWrcYUk Yk+89/7C5VZvHVkv453mbcpMostz4UddeknfAJnvcP/RyMnEpCuP9//GXhJ8CnT7Na eLq5UlIcIHnug== Date: Sat, 23 May 2026 13:03:32 +0300 From: Mike Rapoport To: Kiryl Shutsemau 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, linux-man@vger.kernel.org, alx@kernel.org, "Kiryl Shutsemau (Meta)" Subject: Re: [PATCH v3 05/16] mm: add MM_CP_UFFD_RWP change_protection() flag Message-ID: References: <20260522133857.552279-1-kirill@shutemov.name> <20260522133857.552279-6-kirill@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260522133857.552279-6-kirill@shutemov.name> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 77EA7C000E X-Stat-Signature: hnkfuokei1hfeg8bs7qesgu1ms4gnxxg X-Rspam-User: X-HE-Tag: 1779530625-590630 X-HE-Meta: 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 ENN8PzMb XYeVOMSxfG83AqsHWM5LLb8cn/YHaHGlZQ5WQXTFjjIu3gimaFJ9qH4nlPVU1paOOtWpRG6A9wO6DOqNuXc7seGdxSQV7l/Mhrreoyi15YJeotN3hze/Uts+iawCAS/lhTS2xaxVoW4hOd+lfFV5aHrYJMkxYazPUhneq/z6X7VVjOB9ZYcYLn3i86IJ9hKOjwZpqLkc4C4f1U7s0MLH7MbvO2C1rspAkTAXxfFcneENvJVzzoYIvseiPnF0KuNu+FFOoHjXbb9mI+eaa05GsX//WOOxv0iLHGnxB+0diljkHmevCiz6fd2evEd7XqPx9KxBR3hbkrdsOh+Q= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 22, 2026 at 02:38:46PM +0100, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > Preparatory patch. Add the change_protection() primitive that > userfaultfd RWP will use. > > An RWP-protected PTE is PAGE_NONE with the uffd PTE bit set. The > PROT_NONE half makes the CPU fault on any access; the uffd bit > distinguishes an RWP fault from a plain mprotect(PROT_NONE) or NUMA > hinting fault. MM_CP_UFFD_WP and MM_CP_UFFD_RWP share the same PTE > bit, so the two cannot be used together on the same range. > > Two new change_protection() flags: > > MM_CP_UFFD_RWP install PAGE_NONE and set the uffd bit > MM_CP_UFFD_RWP_RESOLVE restore vma->vm_page_prot, clear the uffd bit > > Both are wired through change_pte_range(), change_huge_pmd(), and > hugetlb_change_protection() so anon, shmem, THP, and hugetlb all > share the same semantics. > > Signed-off-by: Kiryl Shutsemau > Assisted-by: Claude:claude-opus-4-6 Reviewed-by: Mike Rapoport (Microsoft) > --- > include/linux/mm.h | 5 ++++ > include/linux/userfaultfd_k.h | 1 - > mm/huge_memory.c | 30 +++++++++++++---------- > mm/hugetlb.c | 25 ++++++++++++++----- > mm/mprotect.c | 46 +++++++++++++++++++++++++++-------- > 5 files changed, 77 insertions(+), 30 deletions(-) -- Sincerely yours, Mike.