selftests: fix kvm relocatable native/cross builds and installs

kvm test Makefile doesn't fully support cross-builds and installs.
UNAME_M = $(shell uname -m) variable is used to define the target
programs and libraries to be built from arch specific sources in
sub-directories.

For cross-builds to work, UNAME_M has to map to ARCH and arch specific
directories and targets in this Makefile.

UNAME_M variable to used to run the compiles pointing to the right arch
directories and build the right targets for these supported architectures.

TEST_GEN_PROGS and LIBKVM are set using UNAME_M variable.
LINUX_TOOL_ARCH_INCLUDE is set using ARCH variable.

x86_64 targets are named to include x86_64 as a suffix and directories
for includes are in x86_64 sub-directory. s390x and aarch64 follow the
same convention. "uname -m" doesn't result in the correct mapping for
s390x and aarch64. Fix it to set UNAME_M correctly for s390x and aarch64
cross-builds.

In addition, Makefile doesn't create arch sub-directories in the case of
relocatable builds and test programs under s390x and x86_64 directories
fail to build. This is a problem for native and cross-builds. Fix it to
create all necessary directories keying off of TEST_GEN_PROGS.

The following use-cases work with this change:

Native x86_64:
make O=/tmp/kselftest -C tools/testing/selftests TARGETS=kvm install \
 INSTALL_PATH=$HOME/x86_64

arm64 cross-build:
make O=$HOME/arm64_build/ ARCH=arm64 HOSTCC=gcc \
	CROSS_COMPILE=aarch64-linux-gnu- defconfig

make O=$HOME/arm64_build/ ARCH=arm64 HOSTCC=gcc \
	CROSS_COMPILE=aarch64-linux-gnu- all

make kselftest-install TARGETS=kvm O=$HOME/arm64_build ARCH=arm64 \
	HOSTCC=gcc CROSS_COMPILE=aarch64-linux-gnu-

s390x cross-build:
make O=$HOME/s390x_build/ ARCH=s390 HOSTCC=gcc \
	CROSS_COMPILE=s390x-linux-gnu- defconfig

make O=$HOME/s390x_build/ ARCH=s390 HOSTCC=gcc \
	CROSS_COMPILE=s390x-linux-gnu- all

make kselftest-install TARGETS=kvm O=$HOME/s390x_build/ ARCH=s390 \
	HOSTCC=gcc CROSS_COMPILE=s390x-linux-gnu- all

No regressions in the following use-cases:
make -C tools/testing/selftests TARGETS=kvm
make kselftest-all TARGETS=kvm
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/kvm/Makefile

@@ -5,8 +5,34 @@ all:
 
 top_srcdir = ../../../..
 KSFT_KHDR_INSTALL := 1
+
+# For cross-builds to work, UNAME_M has to map to ARCH and arch specific
+# directories and targets in this Makefile. "uname -m" doesn't map to
+# arch specific sub-directory names.
+#
+# UNAME_M variable to used to run the compiles pointing to the right arch
+# directories and build the right targets for these supported architectures.
+#
+# TEST_GEN_PROGS and LIBKVM are set using UNAME_M variable.
+# LINUX_TOOL_ARCH_INCLUDE is set using ARCH variable.
+#
+# x86_64 targets are named to include x86_64 as a suffix and directories
+# for includes are in x86_64 sub-directory. s390x and aarch64 follow the
+# same convention. "uname -m" doesn't result in the correct mapping for
+# s390x and aarch64.
+#
+# No change necessary for x86_64
 UNAME_M := $(shell uname -m)
 
+# Set UNAME_M for arm64 compile/install to work
+ifeq ($(ARCH),arm64)
+	UNAME_M := aarch64
+endif
+# Set UNAME_M s390x compile/install to work
+ifeq ($(ARCH),s390)
+	UNAME_M := s390x
+endif
+
 LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c lib/test_util.c
 LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c
 LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
@@ -53,7 +79,7 @@ LIBKVM += $(LIBKVM_$(UNAME_M))
 INSTALL_HDR_PATH = $(top_srcdir)/usr
 LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
 LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
-LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/x86/include
+LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
 CFLAGS += -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 \
@@ -84,6 +110,7 @@ $(LIBKVM_OBJ): $(OUTPUT)/%.o: %.c
 $(OUTPUT)/libkvm.a: $(LIBKVM_OBJ)
 	$(AR) crs $@ $^
 
+x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
 all: $(STATIC_LIBS)
 $(TEST_GEN_PROGS): $(STATIC_LIBS)