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Merge patch series "Fix RISC-V toolchain extension support detection"

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Conor Dooley <conor@kernel.org> says:

From: Conor Dooley <conor.dooley@microchip.com>

This came up due to a report from Kevin @ kernel-ci, who had been
running a mixed configuration of GNU binutils and clang. Their compiler
was relatively recent & supports Zicbom but binutils @ 2.35.2 did not.

Our current checks for extension support only cover the compiler, but it
appears to me that we need to check both the compiler & linker support
in case of "pot-luck" configurations that mix different versions of
LD,AS,CC etc.

Linker support does not seem possible to actually check, since the ISA
string is emitted into the object files - so I put in version checks for
that. The checks have gotten a bit ugly since 32 & 64 bit support need
to be checked independently but ahh well.

As I was going, I fell into the trap of there being duplicated checks
for CC support in both the Makefile and Kconfig, so as part of renaming
the Kconfig symbol to TOOLCHAIN_HAS_FOO, I dropped the extra checks in
the Makefile. This has the added advantage of the TOOLCHAIN_HAS_FOO
symbol for Zihintpause appearing in .config.

I pushed out a version of this that specificly checked for assember
support for LKP to test & it looked /okay/ - but I did some more testing
today and realised that this is redudant & have since dropped the as
check.

I tested locally with a fair few different combinations, to try and
cover each of AS, LD, CC missing support for the extension.

* b4-shazam-merge:
  riscv: fix detection of toolchain Zihintpause support
  riscv: fix detection of toolchain Zicbom support

Link: https://lore.kernel.org/r/20221006173520.1785507-1-conor@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Palmer Dabbelt 2022-10-27 15:09:50 -07:00
commit 952b64d666
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3 changed files with 16 additions and 9 deletions
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17
arch/riscv/Kconfig
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@ -411,14 +411,16 @@ config RISCV_ISA_SVPBMT
If you don't know what to do here, say Y.
config CC_HAS_ZICBOM
config TOOLCHAIN_HAS_ZICBOM
bool
default y if 64BIT && $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
default y if 32BIT && $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
default y
depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
depends on LLD_VERSION >= 150000 || LD_VERSION >= 23800
config RISCV_ISA_ZICBOM
bool "Zicbom extension support for non-coherent DMA operation"
depends on CC_HAS_ZICBOM
depends on TOOLCHAIN_HAS_ZICBOM
depends on !XIP_KERNEL && MMU
select RISCV_DMA_NONCOHERENT
select RISCV_ALTERNATIVE
@ -433,6 +435,13 @@ config RISCV_ISA_ZICBOM
If you don't know what to do here, say Y.
config TOOLCHAIN_HAS_ZIHINTPAUSE
bool
default y
depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zihintpause)
depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zihintpause)
depends on LLD_VERSION >= 150000 || LD_VERSION >= 23600
config FPU
bool "FPU support"
default y

6
arch/riscv/Makefile
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@ -59,12 +59,10 @@ toolchain-need-zicsr-zifencei := $(call cc-option-yn, -march=$(riscv-march-y)_zi
riscv-march-$(toolchain-need-zicsr-zifencei) := $(riscv-march-y)_zicsr_zifencei
# Check if the toolchain supports Zicbom extension
toolchain-supports-zicbom := $(call cc-option-yn, -march=$(riscv-march-y)_zicbom)
riscv-march-$(toolchain-supports-zicbom) := $(riscv-march-y)_zicbom
riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZICBOM) := $(riscv-march-y)_zicbom
# Check if the toolchain supports Zihintpause extension
toolchain-supports-zihintpause := $(call cc-option-yn, -march=$(riscv-march-y)_zihintpause)
riscv-march-$(toolchain-supports-zihintpause) := $(riscv-march-y)_zihintpause
riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE) := $(riscv-march-y)_zihintpause
KBUILD_CFLAGS += -march=$(subst fd,,$(riscv-march-y))
KBUILD_AFLAGS += -march=$(riscv-march-y)

2
arch/riscv/include/asm/vdso/processor.h
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@ -21,7 +21,7 @@ static inline void cpu_relax(void)
* Reduce instruction retirement.
* This assumes the PC changes.
*/
#ifdef __riscv_zihintpause
#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
__asm__ __volatile__ ("pause");
#else
/* Encoding of the pause instruction */