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b=nLzj7OCGbAYQphViYclXtHITMmaEevm6G40K5z5oGF8OxchRHxEKKiPboc7ARFeiq E1aWmqls8XpEIW6+93ygxdQGIXL8Q3EjpR/7xVLB710yIvO6tcTx/KKn/wAc24xA/X aEq1Yv9XwNS5lbmC1lexYYQDitbtWDngkVPHuUYbjpsuscfMfP5YssJ60G/ZzVSFYv GMF4sAAQO96eKev9xxg6btXLcKm8b5oGv4CzFzICSsALDvTntxaScC/kNvmBua7NUz RJDFb4/OeQx7kYsv9aD/BiNTS9Ar5294YKFIq/uV+B7z4ijcE2KS6aRrt4W+WAIob2 zz7a/yt8o2Xyw== From: SeongJae Park To: Kiryl Shutsemau 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, "Kiryl Shutsemau (Meta)" Subject: Re: [PATCH v5 09/18] mm: add MM_CP_UFFD_RWP change_protection() flag Date: Thu, 28 May 2026 18:19:34 -0700 Message-ID: <20260529011935.8433-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260526130509.2748441-10-kirill@shutemov.name> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Stat-Signature: xscnb3xubcoefsi69b9emksezfdbz8o6 X-Rspam-User: X-Rspamd-Queue-Id: 7266FA0005 X-HE-Tag: 1780017582-887657 X-HE-Meta: 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 3wt2Y/m7 lv6bBANAKGuokoHb0vXPmcT0X4jZ/Vq0UWkUdYqjPdLYoxsPA6P+6MHxT0zAKyqXPTy3W2QjSOHcBfsrEzXvnYyOm49VmOPMXtOm3+dLyEGNp/3/jTwC2psDDqyfypb5PwVMzytSUmy/PeA/x4f4lHYhrlfkv0jGG5HbSzn1SFFmRrRSyng3Kxl57pOEolZ1QvABpZCdtmNoTKhhO66+ZsGCvhOQMp5mv4uAVrXH/IaLswXr30N4Au5F28+vtuaGW98nJ2GjwJmCuHXHnakP8pDGjhinQjfUfktmX0rpBL5TGMM3lI2kN6AuYI6au/RRL6YpgABygeyk6cdA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 26 May 2026 14:04:57 +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) Reviewed-by: SeongJae Park > --- > 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(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 6499cfb61dc4..f79801816f32 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3297,6 +3297,11 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); > #define MM_CP_UFFD_WP_RESOLVE (1UL << 3) /* Resolve wp */ > #define MM_CP_UFFD_WP_ALL (MM_CP_UFFD_WP | \ > MM_CP_UFFD_WP_RESOLVE) > +/* Whether this change is for uffd RWP */ > +#define MM_CP_UFFD_RWP (1UL << 4) /* do rwp */ > +#define MM_CP_UFFD_RWP_RESOLVE (1UL << 5) /* resolve rwp */ > +#define MM_CP_UFFD_RWP_ALL (MM_CP_UFFD_RWP | \ > + MM_CP_UFFD_RWP_RESOLVE) > > bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > pte_t pte); > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > index 0aef628514df..564eb2aac321 100644 > --- a/include/linux/userfaultfd_k.h > +++ b/include/linux/userfaultfd_k.h > @@ -361,7 +361,6 @@ static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma, > return false; > } > > - Nice cleanup. Thanks, SJ [...]