Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte

From	Catalin Marinas <catalin.marinas@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte
Date	2017-09-07 18:50 +0200
Message-ID	<un8a5-2Cg-5@gated-at.bofh.it> (permalink)
References	<ukuqu-3ZB-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Aug 31, 2017 at 06:56:23PM +0900, Masahiro Yamada wrote:
> Aarch64 instructions must be word aligned.  The current 16 byte
> alignment is more than enough.  Relax it into 4 byte alignment.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
> I do not know why arm64 Linux requires 16 byte alignment.
> 
> I dug git-history of arch/arm64/include/asm/linkage.h
> and the only commit I see is:
> 
>   commit aeed41a9371ee02257b608eb06a9058507a7d0f4
>   Author: Marc Zyngier <Marc.Zyngier@arm.com>
>   Date:   Fri Oct 19 17:33:27 2012 +0100
> 
>       arm64: fix alignment padding in assembly code
> 
> It just opt out of the asm-generic variant to remove 0x90.
> So, the amount of alignment might not be not optimized yet.
> 
> Please correct me if I am missing something.

Not sure why we ended up with 4. Possibly because we forgot the power of
2 difference for arm/arm64.

Queued for 4.14. Thanks.

-- 
Catalin

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[PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-08-31 12:00 +0200
  Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4  byte Lothar Waßmann <LW@KARO-electronics.de> - 2017-08-31 12:30 +0200
    Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4  byte Robin Murphy <robin.murphy@arm.com> - 2017-08-31 12:40 +0200
  Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4  byte Catalin Marinas <catalin.marinas@arm.com> - 2017-09-07 18:50 +0200

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