linux-kernel - Re: [PATCH v4 10/15] x86: Implement ARCH_HAS_KERNEL_FPU

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Date: Fri, 29 Mar 2024 13:02:56 -0500
From: Samuel Holland <samuel.holland@...ive.com>
To: Dave Hansen <dave.hansen@...el.com>,
 Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
 Christoph Hellwig <hch@....de>, loongarch@...ts.linux.dev,
 amd-gfx@...ts.freedesktop.org, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>,
 Thomas Gleixner <tglx@...utronix.de>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 10/15] x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT

On 2024-03-29 12:28 PM, Dave Hansen wrote:
> On 3/29/24 00:18, Samuel Holland wrote:
>> +#
>> +# CFLAGS for compiling floating point code inside the kernel.
>> +#
>> +CC_FLAGS_FPU := -msse -msse2
>> +ifdef CONFIG_CC_IS_GCC
>> +# Stack alignment mismatch, proceed with caution.
>> +# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
>> +# (8B stack alignment).
>> +# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
>> +#
>> +# The "-msse" in the first argument is there so that the
>> +# -mpreferred-stack-boundary=3 build error:
>> +#
>> +#  -mpreferred-stack-boundary=3 is not between 4 and 12
>> +#
>> +# can be triggered. Otherwise gcc doesn't complain.
>> +CC_FLAGS_FPU += -mhard-float
>> +CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
>> +endif
> 
> I was expecting to see this (now duplicate) hunk come _out_ of
> lib/Makefile somewhere in the series.
> 
> Did I miss that, or is there something keeping the duplicate there?

This hunk is removed in patch 15/15, after the conversion of lib/test_fpu.c:

https://lore.kernel.org/linux-kernel/20240329072441.591471-16-samuel.holland@sifive.com/

Regards,
Samuel