From:   David Laight <David.Laight@ACULAB.COM>
To:     'Huacai Chen' <chenhuacai@loongson.cn>,
        Arnd Bergmann <arnd@arndb.de>,
        Huacai Chen <chenhuacai@kernel.org>
CC:     "loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Guo Ren <guoren@kernel.org>, Xuerui Wang <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] LoongArch: Make -mstrict-align be configurable
Thread-Topic: [PATCH] LoongArch: Make -mstrict-align be configurable
Thread-Index: AQHZNuKTZOpLs+GXMEuRBwFbIvBWLq67WwCQ
Date:   Thu, 2 Feb 2023 09:01:34 +0000
Message-ID: <363cd09a5dcb4deab21f58c19025254f@AcuMS.aculab.com>
References: <20230202084238.2408516-1-chenhuacai@loongson.cn>
In-Reply-To: <20230202084238.2408516-1-chenhuacai@loongson.cn>
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From: Huacai Chen
> Sent: 02 February 2023 08:43
> 
> Introduce Kconfig option ARCH_STRICT_ALIGN to make -mstrict-align be
> configurable.
> 
> Not all LoongArch cores support h/w unaligned access, we can use the
> -mstrict-align build parameter to prevent unaligned accesses.
> 
> This option is disabled by default to optimise for performance, but you
> can enabled it manually if you want to run kernel on systems without h/w
> unaligned access support.

Should there be an associated run-time check during kernel initialisation
that a kernel compiled without -mstrict-align isn't being run on hardware
that doesn't support unaligned accesses.

It can be quite a while before you get a compiler-generated misaligned accesses.

Also isn't there a HAVE_EFFICIENT_MISALIGNED_ACCESS define that would
also need to be set correctly??

	David

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