Some SSE instructions assume a 16-byte aligned stack, and GCC compiles assuming the stack is aligned: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838. This combination results in a #GP in guests. Adding this compiler flag will generate an alternate prologue and epilogue to realign the runtime stack, which makes selftest code slower and bigger, but this is okay since we do not need selftest code to be extremely performant. Similar issue discussed at https://lore.kernel.org/all/CAGtprH9yKvuaF5yruh3BupQe4BxDGiBQk3ExtY2m39yP-tppsg@xxxxxxxxxxxxxx/ Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx> --- tools/testing/selftests/kvm/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 317927d9c55bd..5f9cc1e6ee67e 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -205,7 +205,7 @@ LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/x86/include else LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include endif -CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \ +CFLAGS += -mstackrealign -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \ -fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \ -I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \ -I$(<D) -Iinclude/$(UNAME_M) -I ../rseq -I.. $(EXTRA_CFLAGS) \ -- 2.39.0.246.g2a6d74b583-goog
