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Subject[PATCH v2 1/4] s390: only build for new CPUs with clang
Date
llvm does does not understand -march=z9-109 and older target
specifiers, so disable the respective Kconfig settings and
the logic to make the boot code work on old systems when
building with clang.

Part of the early boot code is normally compiled with -march=z900
for maximum compatibility. This also has to get changed with
clang to the oldest supported ISA, which is -march=z10 here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/s390/Kconfig | 6 ++++++
arch/s390/boot/Makefile | 18 ++++++++++++------
2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 8cd860cba4d1..1a2eec61196d 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -240,6 +240,7 @@ choice

config MARCH_Z900
bool "IBM zSeries model z800 and z900"
+ depends on !CC_IS_CLANG
select HAVE_MARCH_Z900_FEATURES
help
Select this to enable optimizations for model z800/z900 (2064 and
@@ -248,6 +249,7 @@ config MARCH_Z900

config MARCH_Z990
bool "IBM zSeries model z890 and z990"
+ depends on !CC_IS_CLANG
select HAVE_MARCH_Z990_FEATURES
help
Select this to enable optimizations for model z890/z990 (2084 and
@@ -256,6 +258,7 @@ config MARCH_Z990

config MARCH_Z9_109
bool "IBM System z9"
+ depends on !CC_IS_CLANG
select HAVE_MARCH_Z9_109_FEATURES
help
Select this to enable optimizations for IBM System z9 (2094 and
@@ -347,12 +350,15 @@ config TUNE_DEFAULT

config TUNE_Z900
bool "IBM zSeries model z800 and z900"
+ depends on !CC_IS_CLANG

config TUNE_Z990
bool "IBM zSeries model z890 and z990"
+ depends on !CC_IS_CLANG

config TUNE_Z9_109
bool "IBM System z9"
+ depends on !CC_IS_CLANG

config TUNE_Z10
bool "IBM System z10"
diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile
index c844eaf24ed7..c6a6b6dd3d52 100644
--- a/arch/s390/boot/Makefile
+++ b/arch/s390/boot/Makefile
@@ -12,18 +12,24 @@ KBUILD_AFLAGS := $(KBUILD_AFLAGS_DECOMPRESSOR)
KBUILD_CFLAGS := $(KBUILD_CFLAGS_DECOMPRESSOR)

#
-# Use -march=z900 for als.c to be able to print an error
+# Use minimum architecture for als.c to be able to print an error
# message if the kernel is started on a machine which is too old
#
-ifneq ($(CC_FLAGS_MARCH),-march=z900)
+ifndef CONFIG_CC_IS_CLANG
+CC_FLAGS_MARCH_MINIMUM := -march=z900
+else
+CC_FLAGS_MARCH_MINIMUM := -march=z10
+endif
+
+ifneq ($(CC_FLAGS_MARCH),$(CC_FLAGS_MARCH_MINIMUM))
AFLAGS_REMOVE_head.o += $(CC_FLAGS_MARCH)
-AFLAGS_head.o += -march=z900
+AFLAGS_head.o += $(CC_FLAGS_MARCH_MINIMUM)
AFLAGS_REMOVE_mem.o += $(CC_FLAGS_MARCH)
-AFLAGS_mem.o += -march=z900
+AFLAGS_mem.o += $(CC_FLAGS_MARCH_MINIMUM)
CFLAGS_REMOVE_als.o += $(CC_FLAGS_MARCH)
-CFLAGS_als.o += -march=z900
+CFLAGS_als.o += $(CC_FLAGS_MARCH_MINIMUM)
CFLAGS_REMOVE_sclp_early_core.o += $(CC_FLAGS_MARCH)
-CFLAGS_sclp_early_core.o += -march=z900
+CFLAGS_sclp_early_core.o += $(CC_FLAGS_MARCH_MINIMUM)
endif

CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
--
2.20.0
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