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

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Message-ID: <20200924135429.GC13973@alpha.franken.de>
Date:   Thu, 24 Sep 2020 15:54:29 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Philippe Mathieu-Daudé <f4bug@...at.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        open list <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>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH 4.19 66/81] MIPS: Disable Loongson MMI instructions for
 kernel build

On Mon, Sep 07, 2020 at 05:35:26AM +0200, Philippe Mathieu-Daudé wrote:
> On Thu, Sep 3, 2020 at 11:28 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Wed, Aug 26, 2020 at 02:06:28PM -0700, Guenter Roeck wrote:
> > > 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 ?
> >
> > I don't know, sorry, that would be something that Paul understands.
> >
> > Paul?
> 
> Cc'ing Thomas who now maintains this.

I've queued a patch to fix this in mips-fixes.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]