Re: stable-rc: 5.10: riscv: defconfig: clang-nightly: build failed - Invalid or unknown z ISA extension: 'zifencei'

[Nathan Chancellor <nathan@kernel.org>]

On Tue, Feb 21, 2023 at 09:15:11AM +0000, Conor Dooley wrote:
> On Tue, Feb 21, 2023 at 02:30:17PM +0530, Naresh Kamboju wrote:
> > The riscv defconfig and tinyconfig builds failed with clang-nightly
> > due to below build warnings / errors on latest stable-rc 5.10.
> > 
> > Regression on riscv:
> >   - build/clang-nightly-tinyconfig - FAILED
> >   - build/clang-nightly-defconfig - FAILED
> 
> > Build log:
> > ----
> > make --silent --keep-going --jobs=8
> > O=/home/tuxbuild/.cache/tuxmake/builds/1/build ARCH=riscv
> > CROSS_COMPILE=riscv64-linux-gnu- HOSTCC=clang CC=clang LLVM=1
> > LLVM_IAS=1 LD=riscv64-linux-gnu-ld
> > riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_zicsr2p0_zifencei2p0:
> > Invalid or unknown z ISA extension: 'zifencei'
> > riscv64-linux-gnu-ld: failed to merge target specific data of file
> > init/version.o
> > riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_zicsr2p0_zifencei2p0:
> > Invalid or unknown z ISA extension: 'zifencei'
> > riscv64-linux-gnu-ld: failed to merge target specific data of file
> > init/do_mounts.o
> > riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_zicsr2p0_zifencei2p0:
> > Invalid or unknown z ISA extension: 'zifencei'
> > riscv64-linux-gnu-ld: failed to merge target specific data of file
> > init/noinitramfs.o
> > riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_zicsr2p0_zifencei2p0:
> > Invalid or unknown z ISA extension: 'zifencei'
> > riscv64-linux-gnu-ld: failed to merge target specific data of file
> > init/calibrate.o
> > riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_zicsr2p0_zifencei2p0:
> > Invalid or unknown z ISA extension: 'zifencei'
> 
> > Build details,
> > https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-5.10.y/build/v5.10.168-58-g7d11e4c4fc56/testrun/14869376/suite/build/test/clang-nightly-tinyconfig/details/
> 
> binutils 2.35 by the looks of things, I **think** that zifencei didn't
> land until 2.36. zicsr and zifence get added via cc-option-yn, which,
> IIRC, doesn't do anything with the linker. I dunno if anyone in RISC-V
> land cares this much about "odd" configurations back in 5.10, but while
> a fix is outstanding, you could use a newer binutils?

This is new in clang-17 so I bisected LLVM down to commit 22e199e6afb1
("[RISCV] Accept zicsr and zifencei command line options"), so I think
we need something like commit aae538cd03bc ("riscv: fix detection of
toolchain Zihintpause support") for zifencei to make sure all three
tools stay in sync, since I suspect that this is reproducible in
mainline with GNU ld. We just happen not to notice when using
LLVM=1 LLVM_IAS=1 since the tools have symmetrical support.

I can work up something like that change tomorrow if that seems like the
path worth taking.

Cheers,
Nathan

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