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@xxxxxxxxxxxxx>
---
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@xxxxxxxxxx>
