Re: [PATCH 5.4-rc1 BUILD FIX] s390: mark __cpacf_query() as __always_inline

Heiko Carstens
2019-10-02T08:22:08Z

On Wed, Oct 02, 2019 at 09:03:33AM +0200, Michal Kubecek wrote:
> On Wed, Oct 02, 2019 at 08:46:05AM +0200, Heiko Carstens wrote:
> > On Tue, Oct 01, 2019 at 10:08:01PM +0200, Jiri Kosina wrote:
> > >
> > > In file included from arch/s390/kvm/kvm-s390.c:44:
> > > ./arch/s390/include/asm/cpacf.h: In function '__cpacf_query':
> > > ./arch/s390/include/asm/cpacf.h:179:2: warning: asm operand 3 probably doesn't match constraints
> > > 179 | asm volatile(
> > > | ^~~
> > > ./arch/s390/include/asm/cpacf.h:179:2: error: impossible constraint in 'asm'
> > >
> > > ...
> > >
> > > I am wondering how is it possible that none of the build-testing
> > > infrastructure we have running against linux-next caught this? Not enough
> > > non-x86 coverage?
> >
> > Well, there is plenty of s390 coverage with respect to daily builds
> > (also here). It doesn't fail for me with gcc 9.1; so you may either
> > have a different gcc version or different config options(?) so the
> > compiler decided to not inline the function.
>
> I think I found the reason: we only hit the build failure with one
> special config used for zfcpdump which has
>
> CONFIG_CC_OPTIMIZE_FOR_SIZE=y
>
> When I switched to CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y (which we have
> in other s390x configs and which most people probably prefer), the build
> does not fail even without the patch.

Yes, with CONFIG_CC_OPTIMIZE_FOR_SIZE=y I can see plenty of _additional_
compile failures on s390 with "defconfig". Will fix them all...

Thanks for reporting!