linux-kernel - Re: [PATCH 4.19 66/81] MIPS: Disable Loongson MMI instructions for kernel build

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Date:   Wed, 26 Aug 2020 14:06:28 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Paul Burton <paul.burton@...s.com>,
        Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH 4.19 66/81] MIPS: Disable Loongson MMI instructions for
 kernel build

Hi,

On Wed, Oct 16, 2019 at 02:51:17PM -0700, Greg Kroah-Hartman wrote:
> From: Paul Burton <paul.burton@...s.com>
> 
> commit 2f2b4fd674cadd8c6b40eb629e140a14db4068fd upstream.
> 
> GCC 9.x automatically enables support for Loongson MMI instructions when
> using some -march= flags, and then errors out when -msoft-float is
> specified with:
> 
>   cc1: error: ‘-mloongson-mmi’ must be used with ‘-mhard-float’
> 
> The kernel shouldn't be using these MMI instructions anyway, just as it
> doesn't use floating point instructions. Explicitly disable them in
> order to fix the build with GCC 9.x.
> 

I still see this problem when trying to compile fuloong2e_defconfig with
gcc 9.x or later. Reason seems to be that the patch was applied to
arch/mips/loongson64/Platform, but fuloong2e_defconfig uses
arch/mips/loongson2ef/Platform.

Am I missing something ?

Thanks,
Guenter