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[209.85.220.65]) by mx.google.com with SMTPS id y4sor1561257pfn.64.2019.03.18.09.08.59 for (Google Transport Security); Mon, 18 Mar 2019 09:08:59 -0700 (PDT) Received-SPF: pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=oxnKC1Tg; spf=pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=andreyknvl@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=4jnBV7KXAwRH/SBiWunplsgAO5XC9ZDTjIPOKm8iM+g=; b=oxnKC1TgVy0AfRUFzdhntQ4TnaWjo/dHSXwb/USSzN9iByb1J8qb9RNkXwR6mHS+mw U0ldrfn6mRkKtGFn2Svuia32YqyzgHr8lgGpA8Ip0euwMX1zgcj9IEez46oWi1IBddSU gwBvQTSUaqVbn9YXiSr6jTBOA8Xv5UO8CN9pXByf2+OfL6o1mjVRgyqe5P+Xg2G+PiCf NrrQ0yX3K59cnkolhi014Qa1wO07CtueVQk+/0EtrVmsp+hp6aDS9QuNbVuDWXjtk1vJ lpuGAyImKDa6JNaKflwTKUzEOC9JqWe+LJv/B30MBc7OlHCI7rVxIEK1sErhlvMqw4PK B6tw== X-Google-Smtp-Source: APXvYqz4X+86iXGnn3Nho9z6FaNxwbl9pQbIbD8Gz0QIEPwnGUaSMpR4psZ3WXMcGuMVMNFbcG/Runz5qQVKQSjPXF0= X-Received: by 2002:a62:4299:: with SMTP id h25mr19703730pfd.165.1552925338999; Mon, 18 Mar 2019 09:08:58 -0700 (PDT) MIME-Version: 1.0 References: <56d3373c1c5007d776fcd5de4523f4b9da341fb6.1552679409.git.andreyknvl@google.com> <04c5b2de-7fde-7625-9d42-228160879ea0@gmail.com> In-Reply-To: From: Andrey Konovalov Date: Mon, 18 Mar 2019 17:08:48 +0100 Message-ID: Subject: Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive To: Eric Dumazet Cc: Eric Dumazet , Catalin Marinas , Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , Linux ARM , "open list:DOCUMENTATION" , Linux Memory Management List , linux-arch , netdev , bpf , "open list:KERNEL SELFTEST FRAMEWORK" , LKML , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Mar 18, 2019 at 3:45 PM Eric Dumazet wrote: > > On Mon, Mar 18, 2019 at 6:17 AM Andrey Konovalov wrote: > > > > > Looking at the code, what's the point of this address != zc->address > > check? Should I just remove it? > > No you must not remove it. > > The test detects if a u64 ->unsigned long conversion might have truncated bits. > > Quite surprisingly some people still use 32bit kernels. > > The ABI is 64bit only, because we did not want to have yet another compat layer. > > struct tcp_zerocopy_receive { > __u64 address; /* in: address of mapping */ > __u32 length; /* in/out: number of bytes to map/mapped */ > __u32 recv_skip_hint; /* out: amount of bytes to skip */ > }; Ah, got it, thanks! I'll add a comment here then, otherwise this looks confusing.