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Date:   Tue, 01 Dec 2020 21:49:15 -0800
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Subject: Re: [PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC
To:     Nick Desaulniers <ndesaulniers@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>
CC:     David Woodhouse <dwmw2@infradead.org>, x86@kernel.org,
        Nathan Chancellor <natechancellor@gmail.com>,
        linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
From:   hpa@zytor.com
Message-ID: <E9235D82-F8D5-43E0-B990-C2F0410A997C@zytor.com>
Precedence: bulk

On November 30, 2020 5:13:06 PM PST, Nick Desaulniers <ndesaulniers@google=
=2Ecom> wrote:
>A revert of the following two commits=2E
>commit de3accdaec88 ("x86, build: Build 16-bit code with -m16 where
>possible")
>commit a9cfccee6604 ("x86, build: Change code16gcc=2Eh from a C header to
>an assembly header")
>
>Since commit 0bddd227f3dc ("Documentation: update for gcc 4=2E9
>requirement") the minimum supported version of GCC is gcc-4=2E9=2E  It's
>now
>safe to remove this code=2E
>
>Signed-off-by: Nick Desaulniers <ndesaulniers@google=2Ecom>
>---
> arch/x86/Makefile         |  9 +--------
> arch/x86/boot/code16gcc=2Eh | 12 ------------
> 2 files changed, 1 insertion(+), 20 deletions(-)
> delete mode 100644 arch/x86/boot/code16gcc=2Eh
>
>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>index 1bf21746f4ce=2E=2E7116da3980be 100644
>--- a/arch/x86/Makefile
>+++ b/arch/x86/Makefile
>@@ -24,14 +24,7 @@ endif
>=20
># How to compile the 16-bit code=2E  Note we always compile for
>-march=3Di386;
> # that way we can complain to the user if the CPU is insufficient=2E
>-#
>-# The -m16 option is supported by GCC >=3D 4=2E9 and clang >=3D 3=2E5=2E=
 For
>-# older versions of GCC, include an *assembly* header to make sure
>that
>-# gcc doesn't play any games behind our back=2E
>-CODE16GCC_CFLAGS :=3D -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc=2Eh
>-M16_CFLAGS	 :=3D $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
>-
>-REALMODE_CFLAGS	:=3D $(M16_CFLAGS) -g -Os -DDISABLE_BRANCH_PROFILING \
>+REALMODE_CFLAGS	:=3D -m16 -g -Os -DDISABLE_BRANCH_PROFILING \
> 		   -Wall -Wstrict-prototypes -march=3Di386 -mregparm=3D3 \
> 		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
> 		   -mno-mmx -mno-sse
>diff --git a/arch/x86/boot/code16gcc=2Eh b/arch/x86/boot/code16gcc=2Eh
>deleted file mode 100644
>index e19fd7536307=2E=2E000000000000
>--- a/arch/x86/boot/code16gcc=2Eh
>+++ /dev/null
>@@ -1,12 +0,0 @@
>-/* SPDX-License-Identifier: GPL-2=2E0 */
>-#
>-# code16gcc=2Eh
>-#
>-# This file is added to the assembler via -Wa when compiling 16-bit C
>code=2E
>-# This is done this way instead via asm() to make sure gcc does not
>reorder
>-# things around us=2E
>-#
>-# gcc 4=2E9+ has a real -m16 option so we can drop this hack long term=
=2E
>-#
>-
>-	=2Ecode16gcc

With enthusiasm:

Acked-by: H=2E Peter Anvin <hpa@zytor=2Ecom>
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E