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AJvYcCXDMP/KCsADkleyJ4gmeDtGu+Tc3Ixmq/YAXHvGyl2LlO/83/iAb2caXYbX8FISxk2akfNk0xFTFA==@kvack.org X-Gm-Message-State: AOJu0Yw7qe3fWMsfeOK45f5Zh5d2B21Q5MWDvVerCkDtRwxEvASKrlB1 9XKeAbzjk99PCoX+UKM4A2gHjI6fVr0OnMkQ5hm+PouvvuLE/RiqpgLm1eus+YDS3isBTlVL9Jg rSazpa22DkSozMRmiMw== X-Received: from wrbgw30.prod.google.com ([2002:a05:6000:40de:b0:439:ac29:98cb]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a17:907:6d22:b0:b93:3792:4b03 with SMTP id a640c23a62f3a-b972e4f775amr187595066b.32.1773244898034; Wed, 11 Mar 2026 09:01:38 -0700 (PDT) Date: Wed, 11 Mar 2026 16:01:36 +0000 In-Reply-To: <20260311120418.GU1687929@ziepe.ca> Mime-Version: 1.0 References: <20260227200848.114019-1-david@kernel.org> <20260227200848.114019-17-david@kernel.org> <20260309142954.GM1687929@ziepe.ca> <61df6369-333c-430a-bd18-c5b1acae68ea@kernel.org> <20260311120418.GU1687929@ziepe.ca> Message-ID: Subject: Re: [PATCH v1 16/16] mm/memory: support VM_MIXEDMAP in zap_special_vma_range() From: Alice Ryhl To: Jason Gunthorpe Cc: "David Hildenbrand (Arm)" , linux-kernel@vger.kernel.org, "linux-mm @ kvack . org" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , David Rientjes , Shakeel Butt , "Matthew Wilcox (Oracle)" , Madhavan Srinivasan , Michael Ellerman , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Jarkko Sakkinen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Greg Kroah-Hartman , "Arve =?utf-8?B?SGrDuG5uZXbDpWc=?=" , Todd Kjos , Christian Brauner , Carlos Llamas , Ian Abbott , H Hartley Sweeten , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Leon Romanovsky , Dimitri Sivanich , Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Andy Lutomirski , Vincenzo Frascino , Eric Dumazet , Neal Cardwell , "David S. Miller" , David Ahern , Jakub Kicinski , Paolo Abeni , Miguel Ojeda , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-sgx@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, x86@kernel.org Content-Type: text/plain; charset="utf-8" X-Rspam-User: X-Stat-Signature: rwsf8a5hm8bb7keex3r46jzcpr9um687 X-Rspamd-Queue-Id: 83FC080018 X-Rspamd-Server: rspam03 X-HE-Tag: 1773244900-5359 X-HE-Meta: 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 2DTzEH1a 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 11, 2026 at 09:04:18AM -0300, Jason Gunthorpe wrote: > On Wed, Mar 11, 2026 at 09:38:45AM +0000, Alice Ryhl wrote: > > It doesn't really make sense to have multiple binder VMAs. What happens > > with Rust Binder is that process A is receiving transactions and has the > > VMA mapped once. > > IIRC the problem is the kernel doesn't guarentee singleton VMAs, > userspace can always clone them with fork or something. Did binder > solve this somehow? The Binder VMA is DONTCOPY, so it will not be present after fork. > Since you can't assume there is only one VMA the locking becomes a > mess to cover all the cases where userspace can trigger a VMA clone. > > address space deals with this internally. > > Thus, zap_special_vma_range() is extremely hard to use. I mean, the hard part about the locking is keeping them in sync. Binder just doesn't do that. Only the original VMA gets pages inserted or zapped. If you create a second VMA, you just get a useless read-only VMA that you can't do anything with. Alice