From: Christoffer Dall <christoffer.dall@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
Russell King <linux@armlinux.org.uk>,
Nicolas Pitre <nico@linaro.org>, Andi Kleen <ak@linux.intel.com>,
Richard Earnshaw <rearnsha@gcc.gnu.org>,
Tamar Christina <tnfchris@gcc.gnu.org>,
"# 3.4.x" <stable@vger.kernel.org>,
Julien Thierry <julien.thierry@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
kvmarm@lists.cs.columbia.edu,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] ARM: kvm: fix building with gcc-8
Date: Mon, 5 Feb 2018 09:33:16 +0100 [thread overview]
Message-ID: <20180205083316.GR21802@cbox> (raw)
In-Reply-To: <CAK8P3a2EFdTcM6U4TU6EZz9vzGKK=hE=8yQ-1eTTxjGMRs5SKQ@mail.gmail.com>
On Sun, Feb 04, 2018 at 09:57:49PM +0100, Arnd Bergmann wrote:
> On Sun, Feb 4, 2018 at 7:45 PM, Christoffer Dall
> <christoffer.dall@linaro.org> wrote:
> > Hi Arnd,
> >
> > On Fri, Feb 02, 2018 at 04:07:34PM +0100, Arnd Bergmann wrote:
> >> In banked-sr.c, we use a top-level '__asm__(".arch_extension virt")'
> >> statement to allow compilation of a multi-CPU kernel for ARMv6
> >> and older ARMv7-A that don't normally support access to the banked
> >> registers.
> >>
> >> This is considered to be a programming error by the gcc developers
> >> and will no longer work in gcc-8, where we now get a build error:
> >>
> >> /tmp/cc4Qy7GR.s:34: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_usr'
> >> /tmp/cc4Qy7GR.s:41: Error: Banked registers are not available with this architecture. -- `mrs r3,ELR_hyp'
> >> /tmp/cc4Qy7GR.s:55: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_svc'
> >> /tmp/cc4Qy7GR.s:62: Error: Banked registers are not available with this architecture. -- `mrs r3,LR_svc'
> >> /tmp/cc4Qy7GR.s:69: Error: Banked registers are not available with this architecture. -- `mrs r3,SPSR_svc'
> >> /tmp/cc4Qy7GR.s:76: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_abt'
> >>
> >> Passign the '-march-armv7ve' flag to gcc works, and is ok here, because
> >> we know the functions won't ever be called on pre-ARMv7VE machines.
> >> Unfortunately, older compiler versions (4.8 and earlier) do not understand
> >> that flag, so we still need to keep the asm around.
> >
> > Does "not understand" mean "ignores" or do we get an error?
>
> We get an error, which is why I used the $(call cc-option) Makefile
> helper to check if the compiler supports it.
>
Right.
> >> Backporting to stable kernels (4.6+) is needed to allow those to be built
> >> with future compilers as well.
> >
> > This builds on the toolchains I have on my machine, so:
> >
> > Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
> >
> > Are you applying this via a tree with other fixes or would you like me
> > to carry it in the kvmarm tree?
>
> Please pick it up in your tree.
>
Will do.
Thanks,
-Christoffer
WARNING: multiple messages have this Message-ID (diff)
From: christoffer.dall@linaro.org (Christoffer Dall)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] ARM: kvm: fix building with gcc-8
Date: Mon, 5 Feb 2018 09:33:16 +0100 [thread overview]
Message-ID: <20180205083316.GR21802@cbox> (raw)
In-Reply-To: <CAK8P3a2EFdTcM6U4TU6EZz9vzGKK=hE=8yQ-1eTTxjGMRs5SKQ@mail.gmail.com>
On Sun, Feb 04, 2018 at 09:57:49PM +0100, Arnd Bergmann wrote:
> On Sun, Feb 4, 2018 at 7:45 PM, Christoffer Dall
> <christoffer.dall@linaro.org> wrote:
> > Hi Arnd,
> >
> > On Fri, Feb 02, 2018 at 04:07:34PM +0100, Arnd Bergmann wrote:
> >> In banked-sr.c, we use a top-level '__asm__(".arch_extension virt")'
> >> statement to allow compilation of a multi-CPU kernel for ARMv6
> >> and older ARMv7-A that don't normally support access to the banked
> >> registers.
> >>
> >> This is considered to be a programming error by the gcc developers
> >> and will no longer work in gcc-8, where we now get a build error:
> >>
> >> /tmp/cc4Qy7GR.s:34: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_usr'
> >> /tmp/cc4Qy7GR.s:41: Error: Banked registers are not available with this architecture. -- `mrs r3,ELR_hyp'
> >> /tmp/cc4Qy7GR.s:55: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_svc'
> >> /tmp/cc4Qy7GR.s:62: Error: Banked registers are not available with this architecture. -- `mrs r3,LR_svc'
> >> /tmp/cc4Qy7GR.s:69: Error: Banked registers are not available with this architecture. -- `mrs r3,SPSR_svc'
> >> /tmp/cc4Qy7GR.s:76: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_abt'
> >>
> >> Passign the '-march-armv7ve' flag to gcc works, and is ok here, because
> >> we know the functions won't ever be called on pre-ARMv7VE machines.
> >> Unfortunately, older compiler versions (4.8 and earlier) do not understand
> >> that flag, so we still need to keep the asm around.
> >
> > Does "not understand" mean "ignores" or do we get an error?
>
> We get an error, which is why I used the $(call cc-option) Makefile
> helper to check if the compiler supports it.
>
Right.
> >> Backporting to stable kernels (4.6+) is needed to allow those to be built
> >> with future compilers as well.
> >
> > This builds on the toolchains I have on my machine, so:
> >
> > Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
> >
> > Are you applying this via a tree with other fixes or would you like me
> > to carry it in the kvmarm tree?
>
> Please pick it up in your tree.
>
Will do.
Thanks,
-Christoffer
next prev parent reply other threads:[~2018-02-05 8:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-02 15:07 [PATCH 1/2] ARM: kvm: fix building with gcc-8 Arnd Bergmann
2018-02-02 15:07 ` Arnd Bergmann
2018-02-02 15:07 ` [PATCH 2/2] ARM: xscale: fix gcc-8 build Arnd Bergmann
2018-02-02 15:07 ` Arnd Bergmann
2018-02-02 16:39 ` Nicolas Pitre
2018-02-02 16:39 ` Nicolas Pitre
2018-02-02 15:55 ` [PATCH 1/2] ARM: kvm: fix building with gcc-8 Robin Murphy
2018-02-02 15:55 ` Robin Murphy
2018-02-02 16:23 ` Robin Murphy
2018-02-02 16:23 ` Robin Murphy
2018-02-02 16:29 ` Arnd Bergmann
2018-02-02 16:29 ` Arnd Bergmann
2018-02-02 16:30 ` Robin Murphy
2018-02-02 16:30 ` Robin Murphy
2018-02-04 18:45 ` Christoffer Dall
2018-02-04 18:45 ` Christoffer Dall
2018-02-04 20:57 ` Arnd Bergmann
2018-02-04 20:57 ` Arnd Bergmann
2018-02-05 8:33 ` Christoffer Dall [this message]
2018-02-05 8:33 ` Christoffer Dall
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