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

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Message-ID: <CAAdtpL5ZPh4dBTVg57iF+PzOGFujvaNFxN4F_nEtAbB+=OGvhg@mail.gmail.com>
Date:   Mon, 7 Sep 2020 05:35:26 +0200
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     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 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.