Re: FAILED: Patch "powerpc: xor_vmx: Add '-mhard-float' to CFLAGS" failed to apply to 5.10-stable tree

[Nathan Chancellor <nathan@kernel.org>]

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On Wed, Mar 27, 2024 at 08:20:07AM -0400, Sasha Levin wrote:
> The patch below does not apply to the 5.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
...
> ------------------ original commit in Linus's tree ------------------
> 
> From 35f20786c481d5ced9283ff42de5c69b65e5ed13 Mon Sep 17 00:00:00 2001
> From: Nathan Chancellor <nathan@kernel.org>
> Date: Sat, 27 Jan 2024 11:07:43 -0700
> Subject: [PATCH] powerpc: xor_vmx: Add '-mhard-float' to CFLAGS

I have attached a backport that will work for 5.15 and earlier. I think
you worked around this conflict in 5.15 by taking 04e85bbf71c9 but I am
not sure that is a smart idea. I think it might just be better to drop
that dependency and apply this version in 5.15.

Cheers,
Nathan

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From c6cb80d94871cbb4ff151f7eb2586cadeb364ef7 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Sat, 27 Jan 2024 11:07:43 -0700
Subject: [PATCH 4.19 to 5.15] powerpc: xor_vmx: Add '-mhard-float' to CFLAGS

commit 35f20786c481d5ced9283ff42de5c69b65e5ed13 upstream.

arch/powerpc/lib/xor_vmx.o is built with '-msoft-float' (from the main
powerpc Makefile) and '-maltivec' (from its CFLAGS), which causes an
error when building with clang after a recent change in main:

  error: option '-msoft-float' cannot be specified with '-maltivec'
  make[6]: *** [scripts/Makefile.build:243: arch/powerpc/lib/xor_vmx.o] Error 1

Explicitly add '-mhard-float' before '-maltivec' in xor_vmx.o's CFLAGS
to override the previous inclusion of '-msoft-float' (as the last option
wins), which matches how other areas of the kernel use '-maltivec', such
as AMDGPU.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/1986
Link: https://github.com/llvm/llvm-project/commit/4792f912b232141ecba4cbae538873be3c28556c
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240127-ppc-xor_vmx-drop-msoft-float-v1-1-f24140e81376@kernel.org
[nathan: Fixed conflicts due to lack of 04e85bbf71c9 in older trees]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/powerpc/lib/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 321cab5c3ea0..bd5012aa94e3 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -67,6 +67,6 @@ obj-$(CONFIG_PPC_LIB_RHEAP) += rheap.o
 obj-$(CONFIG_FTR_FIXUP_SELFTEST) += feature-fixups-test.o
 
 obj-$(CONFIG_ALTIVEC)	+= xor_vmx.o xor_vmx_glue.o
-CFLAGS_xor_vmx.o += -maltivec $(call cc-option,-mabi=altivec)
+CFLAGS_xor_vmx.o += -mhard-float -maltivec $(call cc-option,-mabi=altivec)
 
 obj-$(CONFIG_PPC64) += $(obj64-y)
-- 
2.44.0