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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Sep 2021 13:04:01.2536 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8611c997-becc-42b9-2221-08d971fff64f X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT046.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM9PR08MB6657 Hi Julien and Stefano I found that the "cc-option/cc-option-add" is not working for "-march=xxx" option on a few very common aarch64 compilers. Here is what I got when trying to compile XEN on r82 platform. ``` ``` My gcc compiler version is as follows: ``` Using built-in specs. COLLECT_GCC=aarch64-linux-gnu-gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/aarch64-linux-gnu/9/lto-wrapper Target: aarch64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 9.3.0-17ubuntu1~20.04' --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs --enable-languages=c,ada,c++, go,d,fortran,objc,obj-c++,gm2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-9 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --without-target-system-zlib --enable-libpth-m2 --enable-multiarch --enable-fix-cortex-a53-843419 --disable-werror --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=aarch64-linux-gnu --program-prefix=aarch64-linux-gnu- --includedir=/usr/aarch64-linux-gnu/include Thread model: posix gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) ``` However. even if my gcc compiler is indeed not supporting "-march=armv8-r", above check will not identify it "unrecognized option" and seek to the "-march=armv8.4-a" as expected. See the resulting errors, it still uses "-march=armv8-r": ``` make[3]: Entering directory '/home/penny/FVP/r82/fvp_aemv8r_cortexr82_0.0_6347_gcc6.4/xen/xen' aarch64-linux-gnu-gcc -MMD -MP -MF ./.asm-offsets.s.d -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement -Wno-unused-but-set-variable -Wno-unused-local-typedefs -O1 -fno-omit-frame-pointer -nostdinc -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith -Wvla -pipe -D__XEN__ -include /home/penny/FVP/r82/fvp_aemv8r_cortexr82_0.0_6347_gcc6.4/xen/xen/include/xen/config.h -g -march=armv8-r -mgeneral-regs-only -mno-outline-atomics -I/home/penny/FVP/r82/fvp_aemv8r_cortexr82_0.0_6347_gcc6.4 /xen/xen/include -fno-stack-protector -fno-exceptions -fno-asynchronous-unwind-tables -fcf-protection=none -Wnested-externs '-D__OBJECT_FILE__="asm-offsets.s"' -S -g0 -o asm-offsets.s.new -MQ asm-offsets.s arch/arm/arm64/asm-offsets.c cc1: error: unknown value 'armv8-r' for '-march' cc1: note: valid arguments are: armv8-a armv8.1-a armv8.2-a armv8.3-a armv8.4-a armv8.5-a; did you mean 'armv8-a'? make[3]: *** [Makefile:413: asm-offsets.s] Error 1 ``` And the reason is that in the implementation of "cc-option": To handle this we do a test compile, passing the option-under-test, on a code fragment that will always produce a warning (integer assigned to pointer). We then grep for the option-under-test in the compiler's output, the presence of which would indicate an "unrecognized command-line option" warning/error. ``` cc-option = $(shell if test -z "`echo 'void*p=1;' | \ $(1) $(2) -S -o /dev/null -x c - 2>&1 | grep -- $(2) -`"; \ then echo "$(2)"; else echo "$(3)"; fi ;) ``` Here, that is, we are trying to grep "-march=armv8-r" in output message of the test compile, and since the output message(unknown value 'armv8-r' for '-march') doesn't contain the COMPLETE string, it thought the compiler supported this option, but it actually not... Tracing back to the commit about the implementation of "cc-option", it discards the linux method(using exit code to tell) for dealing with disable-warning options. See https://github.com/xen-project/xen/commit/28f8fb7d2b3fde2f5cbe5526ac4f1c932e3f5d26 for more details. To fix this issue, I could loose the "grep check", instead trying to grep the COMPLETE option string("-march=armv8-r"), only partial(armv8-r) is enough. But, hmmm, the way of greping output message to check is kinds of reliable, IMO, since there is no standard for that. What do you suggest? Cheers --- Penny Zheng diff --git a/xen/arch/arm/arch.mk b/xen/arch/arm/arch.mk index 11caec86ba..d2d71baef4 100644 --- a/xen/arch/arm/arch.mk +++ b/xen/arch/arm/arch.mk @@ -10,6 +10,10 @@ $(call cc-option-add,CFLAGS,CC,-Wnested-externs) CFLAGS-$(CONFIG_ARM_32) += -msoft-float CFLAGS-$(CONFIG_ARM_32) += -mcpu=cortex-a15 +#ifeq ($(CONFIG_ARM64_V8R),y) + CFLAGS-$(CONFIG_ARM_64) += $(call cc-option,$(CC),-march=armv8-r,-march=armv8.4-a) +#endif + CFLAGS-$(CONFIG_ARM_64) += -mcpu=generic CFLAGS-$(CONFIG_ARM_64) += -mgeneral-regs-only # No fp registers etc $(call cc-option-add,CFLAGS-$(CONFIG_ARM_64),CC,-mno-outline-atomics)