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Tue, 25 Mar 2025 23:34:46 -0700 (PDT) MIME-Version: 1.0 References: <20250325121624.523258-1-guoren@kernel.org> <20250325121624.523258-2-guoren@kernel.org> In-Reply-To: From: Guo Ren Date: Wed, 26 Mar 2025 14:34:32 +0800 X-Gmail-Original-Message-ID: X-Gm-Features: AQ5f1JpGXhmRPDvCQOc_Kwk_PFeqm824JtKAYEkQji0TkGjMeyznsoqjkxAkPig Message-ID: Subject: Re: [RFC PATCH V3 01/43] rv64ilp32_abi: uapi: Reuse lp64 ABI interface To: Linus Torvalds 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" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: rk6jm1dc3bema8sfifps1jwph9b3twwd X-Rspam-User: X-Rspamd-Queue-Id: A430D100003 X-Rspamd-Server: rspam08 X-HE-Tag: 1742970889-223143 X-HE-Meta: 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 Dbz38Q/4 xUgZ4dOz+3dTezmjsx4shsI2tAtw7PV42M+XCWWuagsug2HCzRUl6UnhkWxo3WUe2RUCf38iYnNbzEd8mi+ggk1LT0SBy9ZuosQE5e0SMMjNsuRSMi4dqTS9yI2OrmamX1w7QYYKIsHWDsZ+S0lrQMJ6dmotJuZ6P9oLUC18ir70kPTOvzyWZ4kSZeReg8AD11Dmy2Qu4kUEMUzTA9BvCvSSo/66OgaHz46tuWPiT1mgIrr8mQB4KbRqHiV02cb1PR7DFdho/hKEUcDKtrlSmpjqkS3ali8UuXFFyGc+52WRCF3Dtay2bKYwtnHqJdoXTkJVFxCYrXE8i+FP5hfAdXeGWHKU1EO1GlIxINgLiYIMRbn3KjRS2V2dXbPkNWX8FNtZU1Z4KbhbleU+r/aYwW9kml3HHJYVdans+SY+zVAnvIPlvf7IL0RiKIvhlQmKfGEg1Ul1KafOPGCCfHG7Zx4E9kAq2N76oTwpxGsgFyrvGecs= 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 Wed, Mar 26, 2025 at 4:41=E2=80=AFAM Linus Torvalds wrote: > > 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 =3D 32 memory layout to match BITS_PER_LONG =3D 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) I used CONFIG_32BIT in v1 and v2, but I've abandoned them because, based on CONFIG_64BIT, I gain more functionality by inheriting the lp64-abi kernel. I want the full functionality of the CONFIG_64BIT Linux kernel, which can be equivalent, used interchangeably, and seamlessly. > > (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. Thanks for the advice. I'm looking at how to make the compat stuff. --=20 Best Regards Guo Ren