[PATCH 2/2] selftests: export INSTALL_HDR_PATH if using "O" to specify output dir

[Xiaoyao Li <xiaoyao.li@intel.com>]

When build kvm selftests in tools/testing/selftests directory with

	make O=~/kselftests TARGETS=kvm

it fails building some kvm test binaries due to lack of header files,
e.g.,

x86_64/vmx_set_nested_state_test.c: In function ‘set_default_vmx_state’:
x86_64/vmx_set_nested_state_test.c:85:7: error: ‘struct
kvm_nested_state’ has no member named ‘hdr’
  state->hdr.vmx.vmxon_pa = 0x1000;

kvm's Makefile unconditionally thinks kernel headers are installed
in the "kernel-src/usr" with "INSTALL_HDR_PATH = $(top_srcdir)/usr".
However, with "O" is specified, it also takes effect on
"make headers_install", that causes no header files generated in
"kernel-src/usr".

Export INSTALL_HDR_PATH when "O" is specified, so that kvm get the right
kernel headers by checking if INSTALL_HDR_PATH is defined.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 tools/testing/selftests/Makefile     | 6 +++++-
 tools/testing/selftests/kvm/Makefile | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 6ec503912bea..5fd72d955e24 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -116,6 +116,10 @@ ARCH           ?= $(SUBARCH)
 export KSFT_KHDR_INSTALL_DONE := 1
 export BUILD
 
+ifneq (1,$(DEFAULT_INSTALL_HDR_PATH))
+export	INSTALL_HDR_PATH := $(BUILD)/usr
+endif
+
 # build and run gpio when output directory is the src dir.
 # gpio has dependency on tools/gpio and builds tools/gpio
 # objects in the src directory in all cases making the src
@@ -148,7 +152,7 @@ khdr:
 ifeq (1,$(DEFAULT_INSTALL_HDR_PATH))
 	$(MAKE) --no-builtin-rules ARCH=$(ARCH) -C $(top_srcdir) headers_install
 else
-	$(MAKE) --no-builtin-rules INSTALL_HDR_PATH=$$BUILD/usr \
+	$(MAKE) --no-builtin-rules INSTALL_HDR_PATH=$(INSTALL_HDR_PATH) \
 		ARCH=$(ARCH) -C $(top_srcdir) headers_install
 endif
 
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 86797e0242d4..c14d23c978d5 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -44,7 +44,7 @@ TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
 TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))
 LIBKVM += $(LIBKVM_$(UNAME_M))
 
-INSTALL_HDR_PATH = $(top_srcdir)/usr
+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
-- 
2.20.1