linux-kernel - [PATCH 1/2] s390: only build for new CPUs with clang

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Date:   Wed, 10 Apr 2019 22:12:40 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-s390@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Philipp Rudo <prudo@...ux.vnet.ibm.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] s390: only build for new CPUs with clang

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.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/s390/Kconfig       | 6 ++++++
 arch/s390/boot/Makefile | 2 ++
 2 files changed, 8 insertions(+)

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..953a74d04990 100644
--- a/arch/s390/boot/Makefile
+++ b/arch/s390/boot/Makefile
@@ -11,6 +11,7 @@ KASAN_SANITIZE := n
 KBUILD_AFLAGS := $(KBUILD_AFLAGS_DECOMPRESSOR)
 KBUILD_CFLAGS := $(KBUILD_CFLAGS_DECOMPRESSOR)
 
+ifndef CONFIG_CC_IS_CLANG
 #
 # Use -march=z900 for als.c to be able to print an error
 # message if the kernel is started on a machine which is too old
@@ -25,6 +26,7 @@ CFLAGS_als.o			+= -march=z900
 CFLAGS_REMOVE_sclp_early_core.o	+= $(CC_FLAGS_MARCH)
 CFLAGS_sclp_early_core.o	+= -march=z900
 endif
+endif
 
 CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
 
-- 
2.20.0