[PATCH] KVM: selftests: Don't force -march=x86-64-v2 if it's unsupported

[Sean Christopherson]

Force -march=x86-64-v2 to avoid SSE/AVX instructions if and only if the
uarch definition is supported by the compiler, e.g. gcc 7.5 only supports
x86-64.

Fixes: 9a400068a158 ("KVM: selftests: x86: Avoid using SSE/AVX instructions")
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---

My big ol' AVX enabling series ain't looking so bad now ;-)

 tools/testing/selftests/kvm/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 156fbfae940f..5fa282643cff 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -249,8 +249,10 @@ ifeq ($(ARCH),s390)
 	CFLAGS += -march=z10
 endif
 ifeq ($(ARCH),x86)
+ifeq ($(shell echo "void foo(void) { }" | $(CC) -march=x86-64-v2 -x c - -c -o /dev/null 2>/dev/null; echo "$$?"),0)
 	CFLAGS += -march=x86-64-v2
 endif
+endif
 ifeq ($(ARCH),arm64)
 tools_dir := $(top_srcdir)/tools
 arm64_tools_dir := $(tools_dir)/arch/arm64/tools/

base-commit: 81983758430957d9a5cb3333fe324fd70cf63e7e
-- 
2.47.0.163.g1226f6d8fa-goog