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

Started byMasahiro Yamada <yamada.masahiro@socionext.com>
First post2017-09-20 13:00 +0200
Last post2017-09-20 14:20 +0200
Articles 2 — 2 participants

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  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

#1735713 — Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte

FromMasahiro Yamada <yamada.masahiro@socionext.com>
Date2017-09-20 13:00 +0200
SubjectRe: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte
Message-ID<urKTw-1Wj-23@gated-at.bofh.it>
Hi Catalin,


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.

Where was it queued?





-- 
Best Regards
Masahiro Yamada

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#1735746 — Re: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte

FromCatalin Marinas <catalin.marinas@arm.com>
Date2017-09-20 14:20 +0200
SubjectRe: [PATCH] arm64: relax assembly code alignment from 16 byte to 4 byte
Message-ID<urM8V-2U6-9@gated-at.bofh.it>
In reply to#1735713
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

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