From: catalin.marinas@arm.com (Catalin Marinas)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte
Date: Wed, 20 Sep 2017 13:19:07 +0100 [thread overview]
Message-ID: <20170920121907.x4jxd74tuogkb52a@localhost> (raw)
In-Reply-To: <CAK7LNAQYDgY-4Bu9-RRLAj8hvKFXx2ctXFf058W4uQLoqpTQeg@mail.gmail.com>
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
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Rob Herring <robh@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Marc Zyngier <marc.zyngier@arm.com>,
Will Deacon <will.deacon@arm.com>,
Russell King <linux@armlinux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Olof Johansson <olof@lixom.net>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte
Date: Wed, 20 Sep 2017 13:19:07 +0100 [thread overview]
Message-ID: <20170920121907.x4jxd74tuogkb52a@localhost> (raw)
In-Reply-To: <CAK7LNAQYDgY-4Bu9-RRLAj8hvKFXx2ctXFf058W4uQLoqpTQeg@mail.gmail.com>
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
next prev parent reply other threads:[~2017-09-20 12:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 9:56 [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte Masahiro Yamada
2017-08-31 9:56 ` Masahiro Yamada
2017-08-31 10:23 ` Lothar Waßmann
2017-08-31 10:23 ` Lothar Waßmann
2017-08-31 10:38 ` Robin Murphy
2017-08-31 10:38 ` Robin Murphy
2017-09-07 16:46 ` Catalin Marinas
2017-09-07 16:46 ` Catalin Marinas
2017-09-20 10:58 ` Masahiro Yamada
2017-09-20 10:58 ` Masahiro Yamada
2017-09-20 12:19 ` Catalin Marinas [this message]
2017-09-20 12:19 ` Catalin Marinas
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