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. Michal Kubecek
