From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from hall.aurel32.net (hall.aurel32.net [195.154.113.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C4B797B for ; Sat, 11 Mar 2023 09:15:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=aurel32.net ; s=202004.hall; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Content-Transfer-Encoding:From:Reply-To: Subject:Content-ID:Content-Description:X-Debbugs-Cc; bh=oGlz0x3waUETRxmcy9pz+bC50AW+Mj+vbt06v0RUcGI=; b=k8vkyBbcUPKoQCtzQ2jgVV/flg sLhI9zILLXp4T/qCOsob3BNijz3pCsR6e6oUleRMvu2Agn+QG/HLjvmV+YX9BUaFKqPnLcsF/xsH+ yPH9U++3miVB5IjiCG6AkOE/lqGT5EMRoThhfRYRig66Aim1nRmjvPfr2tnIqtkLE+YmeCNL3yssH EQN2MF74lntRkUavlczPBIBXX/iI8FrCJY6/oVTi5lFQYbU1R1vzNjdcVv5G2FE+jb4HeBXXuFDje YjrRKmbHJvFF6S1+FdcRy43CrSXnx8bhUdkX73g0uoydBASnHc2F5Gii0x9WilfgKFlP/st6m91Vk XwYrfmIw==; Received: from [2a01:e34:ec5d:a741:8a4c:7c4e:dc4c:1787] (helo=ohm.rr44.fr) by hall.aurel32.net with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pauy1-00Bga5-4p; Sat, 11 Mar 2023 09:52:41 +0100 Received: from aurel32 by ohm.rr44.fr with local (Exim 4.96) (envelope-from ) id 1pauxz-009Tvm-1c; Sat, 11 Mar 2023 09:52:39 +0100 Date: Sat, 11 Mar 2023 09:52:39 +0100 From: Aurelien Jarno To: Bin Meng Cc: conor@kernel.org, conor.dooley@microchip.com, linux-riscv@lists.infradead.org, llvm@lists.linux.dev, naresh.kamboju@linaro.org, nathan@kernel.org, ndesaulniers@google.com, palmer@dabbelt.com, palmer@rivosinc.com, stable@vger.kernel.org Subject: Re: [PATCH v2] RISC-V: remove I-extension ISA spec version dance Message-ID: References: <20230308220842.1231003-1-conor@kernel.org> <20230310150754.535425-1-bmeng.cn@gmail.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230310150754.535425-1-bmeng.cn@gmail.com> User-Agent: Mutt/2.2.7 (2022-08-07) On 2023-03-10 23:07, Bin Meng wrote: > > From: Conor Dooley > > > > The spec folk, in their infinite wisdom, moved both control and status > > registers & the FENCE.I instructions out of the I extension into their > > own extensions (Zicsr, Zifencei) in the 20190608 version of the ISA > > spec [0]. > > The GCC/binutils crew decided [1] to move their default version of the > > ISA spec to the 20191213 version of the ISA spec, which came into being > > for version 2.38 of binutils and GCC 12. Building with this toolchain > > configuration would result in assembler issues: > > CC arch/riscv/kernel/vdso/vgettimeofday.o > > <>/arch/riscv/include/asm/vdso/gettimeofday.h: Assembler messages: > > <>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01' > > <>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01' > > <>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01' > > <>/arch/riscv/include/asm/vdso/gettimeofday.h:71: Error: unrecognized opcode `csrr a5,0xc01' > > This was fixed in commit 6df2a016c0c8 ("riscv: fix build with binutils > > 2.38") by Aurelien Jarno, but has proven fragile. > > > > Before LLVM 17, LLVM did not support these extensions and, as such, the > > cc-option check added by Aurelien worked. Since commit 22e199e6afb1 > > ("[RISCV] Accept zicsr and zifencei command line options") however, LLVM > > *does* support them and the cc-option check passes. > > > > This surfaced as a problem while building the 5.10 stable kernel using > > the default Tuxmake Debian image [2], as 5.10 did not yet support ld.lld, > > and uses the Debian provided binutils 2.35. > > Versions of ld prior to 2.38 will refuse to link if they encounter > > unknown ISA extensions, and unfortunately Zifencei is not supported by > > bintuils 2.35. > > > > Instead of dancing around with adding these extensions to march, as we > > currently do, Palmer suggested locking GCC builds to the same version of > > the ISA spec that is used by LLVM. As far as I can tell, that is 2.2, > > with, apparently [3], a lack of interest in implementing a flag like > > GCC's -misa-spec at present. > > > > Add {cc,as}-option checks to add -misa-spec to KBUILD_{A,C}FLAGS when > > GCC is used & remove the march dance. > > > > As clang does not accept this argument, I had expected to encounter > > issues with the assembler, as neither zicsr nor zifencei are present in > > the ISA string and the spec version *should* be defaulting to a version > > that requires them to be present. The build passed however and the > > resulting kernel worked perfectly fine for me on a PolarFire SoC... > > > > Link: https://riscv.org/wp-content/uploads/2019/06/riscv-spec.pdf [0] > > Link: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/aE1ZeHHCYf4 [1] > > Link: https://lore.kernel.org/all/CA+G9fYt9T=ELCLaB9byxaLW2Qf4pZcDO=huCA0D8ug2V2+irJQ@mail.gmail.com/ [2] > > Link: https://discourse.llvm.org/t/specifying-unpriviledge-spec-version-misa-spec-gcc-flag-equivalent/66935 [3] > > CC: stable@vger.kernel.org > > Suggested-by: Palmer Dabbelt > > Reported-by: Naresh Kamboju > > Signed-off-by: Conor Dooley > > --- > > I think Aurelien's original commit message might actually not be quite > > correct? I found, in my limited testing, that it is not the default > > behaviour of gas that matters, but rather the toolchain itself? > > My binutils versions (both those built using the clang-built-linux > > tc-build scripts which do not set an ISA spec version, and one built > > using the riscv-gnu-toolchain infra w/ an explicit 20191213 spec version > > set) do not encounter these issues. > > I am unable to reproduce the build failure as reported by commit 6df2a016c0c8 > ("riscv: fix build with binutils 2.38") by Aurelien Jarno using kernel.org > pre-built GCC 11.3.0 [1] which includes binutils 2.38. > > [1] https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/11.3.0/x86_64-gcc-11.3.0-nolibc-x86_64-linux.tar.xz I guess you mean https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/11.3.0/x86_64-gcc-11.3.0-nolibc-riscv64-linux.tar.gz > The defconfig of v5.16 kernel (commit 6df2a016c0c8 lands in v5.17) builds fine > for me. Anything I am missing? I can't find the corresponding source and unfortunately binutils doesn't record the configure options in the binaries, but my guess is that it has been configured with --with-isa-spec=2.2. This is not the recommended way to go, but given the mess many distribution went that road. -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://www.aurel32.net