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[209.85.167.41]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-30d7d557b9fsm19725401fa.0.2025.03.25.13.47.03 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Mar 2025 13:47:04 -0700 (PDT) Received: by mail-lf1-f41.google.com with SMTP id 2adb3069b0e04-54954fa61c9so6938867e87.1 for ; Tue, 25 Mar 2025 13:47:03 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCUioGTQVGskT5qM4f83HrgNHpssFwc1i4C9/bOJz66irRsGSfTvFeW78YhL5aQSO08h7n/K/FWeFw==@kvack.org X-Received: by 2002:a17:907:95a4:b0:ac3:48e4:f8bc with SMTP id a640c23a62f3a-ac3f27fd3b3mr1859596466b.48.1742935307883; Tue, 25 Mar 2025 13:41:47 -0700 (PDT) MIME-Version: 1.0 References: <20250325121624.523258-1-guoren@kernel.org> <20250325121624.523258-2-guoren@kernel.org> In-Reply-To: <20250325121624.523258-2-guoren@kernel.org> From: Linus Torvalds Date: Tue, 25 Mar 2025 13:41:30 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AQ5f1JpwFc7ifwGuAhyrs4E5qPgHx1McCR38KFycRhkLFRMKTveHrmoaWi4zba4 Message-ID: Subject: Re: [RFC PATCH V3 01/43] rv64ilp32_abi: uapi: Reuse lp64 ABI interface To: guoren@kernel.org Cc: arnd@arndb.de, gregkh@linuxfoundation.org, paul.walmsley@sifive.com, palmer@dabbelt.com, anup@brainfault.org, atishp@atishpatra.org, oleg@redhat.com, kees@kernel.org, tglx@linutronix.de, will@kernel.org, mark.rutland@arm.com, brauner@kernel.org, akpm@linux-foundation.org, rostedt@goodmis.org, edumazet@google.com, unicorn_wang@outlook.com, inochiama@outlook.com, gaohan@iscas.ac.cn, shihua@iscas.ac.cn, jiawei@iscas.ac.cn, wuwei2016@iscas.ac.cn, drew@pdp7.com, prabhakar.mahadev-lad.rj@bp.renesas.com, ctsai390@andestech.com, wefu@redhat.com, kuba@kernel.org, pabeni@redhat.com, josef@toxicpanda.com, dsterba@suse.com, mingo@redhat.com, peterz@infradead.org, boqun.feng@gmail.com, xiao.w.wang@intel.com, qingfang.deng@siflower.com.cn, leobras@redhat.com, jszhang@kernel.org, conor.dooley@microchip.com, samuel.holland@sifive.com, yongxuan.wang@sifive.com, luxu.kernel@bytedance.com, david@redhat.com, ruanjinjie@huawei.com, cuiyunhui@bytedance.com, wangkefeng.wang@huawei.com, qiaozhe@iscas.ac.cn, ardb@kernel.org, ast@kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-mm@kvack.org, linux-crypto@vger.kernel.org, bpf@vger.kernel.org, linux-input@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-serial@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, maple-tree@lists.infradead.org, linux-trace-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-atm-general@lists.sourceforge.net, linux-btrfs@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-nfs@vger.kernel.org, linux-sctp@vger.kernel.org, linux-usb@vger.kernel.org, linux-media@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: BC9C5140003 X-Stat-Signature: ikx86xiazopc39u77pyrq4a8wn5e6asm X-HE-Tag: 1742935627-428099 X-HE-Meta: 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 fuq74Gcd 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 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: List-Subscribe: List-Unsubscribe: On Tue, 25 Mar 2025 at 05:17, wrote: > > The rv64ilp32 abi kernel accommodates the lp64 abi userspace and > leverages the lp64 abi Linux interface. Hence, unify the > BITS_PER_LONG = 32 memory layout to match BITS_PER_LONG = 64. No. This isn't happening. You can't do crazy things in the RISC-V code and then expect the rest of the kernel to just go "ok, we'll do crazy things". We're not doing crazy __riscv_xlen hackery with random structures containing 64-bit values that the kernel then only looks at the low 32 bits. That's wrong on *so* many levels. I'm willing to say "big-endian is dead", but I'm not willing to accept this kind of crazy hackery. Not today, not ever. If you want to run a ilp32 kernel on 64-bit hardware (and support 64-bit ABI just in a 32-bit virtual memory size), I would suggest you (a) treat the kernel as natively 32-bit (obviously you can then tell the compiler to use the rv64 instructions, which I presume you're already doing - I didn't look) (b) look at making the compat stuff do the conversion the "wrong way". And btw, that (b) implies *not* just ignoring the high bits. If user-space gives 64-bit pointer, you don't just treat it as a 32-bit one by dropping the high bits. You add some logic to convert it to an invalid pointer so that user space gets -EFAULT. Linus