linux-kernel - Re: [PATCH 1/2] riscv: fix detection of toolchain Zicbom support

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Date:   Thu, 13 Oct 2022 13:22:47 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Conor Dooley <conor@...nel.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Dao Lu <daolu@...osinc.com>, Heiko Stuebner <heiko@...ech.de>,
        Guo Ren <guoren@...nel.org>, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: [PATCH 1/2] riscv: fix detection of toolchain Zicbom support

On Thu, Oct 06, 2022 at 06:35:20PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
> 
> It is not sufficient to check if a toolchain supports a particular
> extension without checking if the linker supports that extension too.
> For example, Clang 15 supports Zicbom but GNU bintutils 2.35.2 does
> not, leading build errors like so:
> 
> riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zicbom1p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zicbom'
> 
> Convert CC_HAS_ZICBOM to TOOLCHAIN_HAS_ZICBOM & check if the linker
> also supports Zicbom.
> 
> Reported-by: Kevin Hilman <khilman@...libre.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1714
> Link: https://storage.kernelci.org/next/master/next-20220920/riscv/defconfig+CONFIG_EFI=n/clang-16/logs/kernel.log
> Fixes: 1631ba1259d6 ("riscv: Add support for non-coherent devices using zicbom extension")
> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>

The versions look correct to me. I see the LLVM zicbom commit [1] in
llvmorg-15.0.0 and I see the binutils zicbom commit [2] in
binutils-2_39.

FWIW, if we are adding explicit tool versions to the Kconfig, could you
not also drop the cc-option checks? Typically, cc-option is only used
when dynamically checking for a feature, in lieu of statically checking
a version. No strong opinion though.

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

[1]: https://github.com/llvm/llvm-project/commit/4f40ca53cefb725aca6564585d0ec4836a79e21a
[2]: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=41d6ac5da655a2e78109848f2db47e53552fd61a

> ---
>  arch/riscv/Kconfig  | 10 ++++++----
>  arch/riscv/Makefile |  3 +--
>  2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index d557cc50295d..6da36553158b 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -401,14 +401,16 @@ config RISCV_ISA_SVPBMT
>  
>  	   If you don't know what to do here, say Y.
>  
> -config CC_HAS_ZICBOM
> +config TOOLCHAIN_HAS_ZICBOM
>  	bool
> -	default y if 64BIT && $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
> -	default y if 32BIT && $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
> +	default y
> +	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
> +	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
> +	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
>  
>  config RISCV_ISA_ZICBOM
>  	bool "Zicbom extension support for non-coherent DMA operation"
> -	depends on CC_HAS_ZICBOM
> +	depends on TOOLCHAIN_HAS_ZICBOM
>  	depends on !XIP_KERNEL && MMU
>  	select RISCV_DMA_NONCOHERENT
>  	select RISCV_ALTERNATIVE
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 3fa8ef336822..3607d38edb4f 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -57,8 +57,7 @@ toolchain-need-zicsr-zifencei := $(call cc-option-yn, -march=$(riscv-march-y)_zi
>  riscv-march-$(toolchain-need-zicsr-zifencei) := $(riscv-march-y)_zicsr_zifencei
>  
>  # Check if the toolchain supports Zicbom extension
> -toolchain-supports-zicbom := $(call cc-option-yn, -march=$(riscv-march-y)_zicbom)
> -riscv-march-$(toolchain-supports-zicbom) := $(riscv-march-y)_zicbom
> +riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZICBOM) := $(riscv-march-y)_zicbom
>  
>  # Check if the toolchain supports Zihintpause extension
>  toolchain-supports-zihintpause := $(call cc-option-yn, -march=$(riscv-march-y)_zihintpause)
> -- 
> 2.37.3
> 
>