linux-kernel - Re: [PATCH] powerpc: Limit ARCH_HAS_KERNEL_FPU

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Date: Wed, 29 May 2024 15:19:57 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: linuxppc-dev@...ts.ozlabs.org, kernel test robot <lkp@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christian König <christian.koenig@....com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Nicholas Piggin <npiggin@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: Limit ARCH_HAS_KERNEL_FPU_SUPPORT to PPC64

On Wed, May 29, 2024 at 09:28:50AM -0700, Samuel Holland wrote:
> When building a 32-bit kernel, some toolchains do not allow mixing soft
> float and hard float object files:
> 
>     LD      vmlinux.o
>   powerpc64le-unknown-linux-musl-ld: lib/test_fpu_impl.o uses hard float, arch/powerpc/kernel/udbg.o uses soft float
>   powerpc64le-unknown-linux-musl-ld: failed to merge target specific data of file lib/test_fpu_impl.o
>   make[2]: *** [scripts/Makefile.vmlinux_o:62: vmlinux.o] Error 1
>   make[1]: *** [Makefile:1152: vmlinux_o] Error 2
>   make: *** [Makefile:240: __sub-make] Error 2
> 
> This is not an issue when building a 64-bit kernel. To unbreak the
> build, limit ARCH_HAS_KERNEL_FPU_SUPPORT to 64-bit kernels. This is okay
> because the only real user of this option, amdgpu, was previously
> limited to PPC64 anyway; see commit a28e4b672f04 ("drm/amd/display: use
> ARCH_HAS_KERNEL_FPU_SUPPORT").
> 
> Fixes: 01db473e1aa3 ("powerpc: implement ARCH_HAS_KERNEL_FPU_SUPPORT")
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202405250851.Z4daYSWG-lkp@intel.com/
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Closes: https://lore.kernel.org/lkml/eeffaec3-df63-4e55-ab7a-064a65c00efa@roeck-us.net/
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>

Tested-by: Guenter Roeck <linux@...ck-us.net>

> ---
> 
>  arch/powerpc/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3c968f2f4ac4..c88c6d46a5bc 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,7 +137,7 @@ config PPC
>  	select ARCH_HAS_GCOV_PROFILE_ALL
>  	select ARCH_HAS_HUGEPD			if HUGETLB_PAGE
>  	select ARCH_HAS_KCOV
> -	select ARCH_HAS_KERNEL_FPU_SUPPORT	if PPC_FPU
> +	select ARCH_HAS_KERNEL_FPU_SUPPORT	if PPC64 && PPC_FPU
>  	select ARCH_HAS_MEMBARRIER_CALLBACKS
>  	select ARCH_HAS_MEMBARRIER_SYNC_CORE
>  	select ARCH_HAS_MEMREMAP_COMPAT_ALIGN	if PPC_64S_HASH_MMU
> -- 
> 2.44.1
>