Messages in this thread | | | Date | Fri, 27 Jan 2023 19:12:55 +0100 | Subject | Re: [RFC PATCH v1] KVM: selftests: Compile s390 tests with -march=z10 | From | Thomas Huth <> |
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On 27/01/2023 18.45, Nina Schoetterl-Glausch wrote: > The guest used in s390 kvm selftests is not be set up to handle all > instructions the compiler might emit, i.e. vector instructions, leading > to crashes. > Limit what the compiler emits to the oldest machine model currently > supported by Linux. > > Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com> > --- > > Should we also set -mtune?
I don't think it's really necessary
> Since it are vector instructions that caused the problem here, there > are some alternatives: > * use -mno-vx > * set the required guest control bit to enable vector instructions on > models supporting them > > -march=z10 might prevent similar issues with other instructions, but I > don't know if there actually exist other relevant instructions, so it > could be needlessly restricting.
FWIW, the vector instructions have been introduced with the z13 ... so limiting to the zEC12 could be enough.
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile > index 1750f91dd936..df0989949eb5 100644 > --- a/tools/testing/selftests/kvm/Makefile > +++ b/tools/testing/selftests/kvm/Makefile > @@ -200,6 +200,9 @@ CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \ > -I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \ > -I$(<D) -Iinclude/$(ARCH_DIR) -I ../rseq -I.. $(EXTRA_CFLAGS) \ > $(KHDR_INCLUDES) > +ifeq ($(ARCH),s390) > + CFLAGS += -march=z10 > +endif
Starting with z10 sounds sane to me, we still can adjust later if necessary.
Reviewed-by: Thomas Huth <thuth@redhat.com>
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