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	2017-09-20 14:20 +0200
Message-ID	<urM8V-2U6-9@gated-at.bofh.it> (permalink)
References	<ukuqu-3ZB-9@gated-at.bofh.it> <un8a5-2Cg-5@gated-at.bofh.it> <urKTw-1Wj-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Wed, Sep 20, 2017 at 07:58:34PM +0900, Masahiro Yamada wrote:
> 2017-09-08 1:46 GMT+09:00 Catalin Marinas <catalin.marinas@arm.com>:
> > 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.
> 
> I still do not see this patch in linux-next.

It won't make it into linux-next now, I'll push it as a fix for -rc2
(sorry, I've been away at Plumbers and didn't get the chance to send any
pull request). I'll push the patch out on fixes/core once I investigate
some unrelated failures.

-- 
Catalin

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-09-20 13:00 +0200
  Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4  byte Catalin Marinas <catalin.marinas@arm.com> - 2017-09-20 14:20 +0200

csiph-web