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From: Arnd Bergmann <arnd@arndb.de>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	llvm@lists.linux.dev,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Christian Biesinger <cbiesinger@google.com>,
	Simon Marchi <simon.marchi@polymtl.ca>
Subject: Re: [PATCH 1/3] arm64: vdso32: drop the test for dmb ishld
Date: Wed, 13 Oct 2021 09:55:14 +0200	[thread overview]
Message-ID: <CAK8P3a3UBEJ0Py2ycz=rHfgog8g3mCOeQOwO0Gmp-iz6Uxkapg@mail.gmail.com> (raw)
In-Reply-To: <20211012234606.91717-2-ndesaulniers@google.com>

On Wed, Oct 13, 2021 at 1:46 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> Binutils added support for this instruction in commit
> e797f7e0b2bedc9328d4a9a0ebc63ca7a2dbbebc which shipped in 2.34 (just
> missing the 2.33 release) but was cherry-picked into 2.33 in commit
> 27a50d6755bae906bc73b4ec1a8b448467f0bea1. Thanks to Christian and Simon
> for helping me with the patch archaeology.
>
> According to Documentation/process/changes.rst, the minimum supported
> version of binutils is 2.33. Since all supported versions of GAS support
> this instruction, drop the assembler invocation, preprocessor
> flags/guards, and the cross assembler macro that's now unused.
>
> This also avoids a recursive self reference in a follow up cleanup
> patch.
>
> Cc: Christian Biesinger <cbiesinger@google.com>
> Cc: Simon Marchi <simon.marchi@polymtl.ca>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

This change looks good, but I think we should do the same for the gcc
version check:

> -#if __LINUX_ARM_ARCH__ >= 8 && defined(CONFIG_AS_DMB_ISHLD)
> +#if __LINUX_ARM_ARCH__ >= 8
>  #define aarch32_smp_mb()       dmb(ish)
>  #define aarch32_smp_rmb()      dmb(ishld)
>  #define aarch32_smp_wmb()      dmb(ishst)

gcc-4.8 already supported -march=armv8, and we require gcc-5.1 now, so both
this #if/#else construct and the corresponding "cc32-option,-march=armv8-a"
check should be obsolete now.

       Arnd

  reply	other threads:[~2021-10-13  7:55 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-12 23:46 [PATCH 0/3] compat vdso cleanups Nick Desaulniers
2021-10-12 23:46 ` [PATCH 1/3] arm64: vdso32: drop the test for dmb ishld Nick Desaulniers
2021-10-13  7:55   ` Arnd Bergmann [this message]
2021-10-13 17:24   ` Christian Biesinger
2021-10-12 23:46 ` [PATCH 2/3] arm64: vdso32: lazily invoke COMPAT_CC Nick Desaulniers
2021-10-13  3:02   ` Masahiro Yamada
2021-10-14 20:59     ` Nick Desaulniers
2021-10-16 14:19       ` Masahiro Yamada
2021-10-18 20:34         ` Nick Desaulniers
2021-10-12 23:46 ` [PATCH 3/3] arm64: vdso32: require CROSS_COMPILE_COMPAT for gcc+bfd Nick Desaulniers
2021-10-18 22:58   ` Nathan Chancellor

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