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Message-Id: <20240507-compile_kernel_with_extensions-v2-7-722c21c328c6@rivosinc.com> Date: Tue, 07 May 2024 18:36:33 -0700 From: Charlie Jenkins <charlie@...osinc.com> To: Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor.dooley@...rochip.com>, Song Liu <song@...nel.org>, Xi Wang <xi.wang@...il.com>, Björn Töpel <bjorn@...osinc.com>, Clément Léger <cleger@...osinc.com>, Jessica Clarke <jrtc27@...c27.com>, Andy Chiu <andy.chiu@...ive.com> Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com> Subject: [PATCH v2 7/8] riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBC Kconfig option Zbc can optimize kernel instruction sequences. Add a config option PLATFORM_SUPPORTS_RISCV_ISA_ZBC that allows arbitrary Zbc instruction sequences to be emitted by the compiler. The existing "RISCV_ISA_ZBC" option is repurposed to be used to by kernel code to determine if either PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBC or PLATFORM_SUPPORTS_RISCV_ISA_ZBC has been set. Signed-off-by: Charlie Jenkins <charlie@...osinc.com> --- arch/riscv/Kconfig.isa | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++ arch/riscv/Makefile | 1 + 2 files changed, 52 insertions(+) diff --git a/arch/riscv/Kconfig.isa b/arch/riscv/Kconfig.isa index e7f28dc44137..b7399f236bba 100644 --- a/arch/riscv/Kconfig.isa +++ b/arch/riscv/Kconfig.isa @@ -289,3 +289,54 @@ config PLATFORM_SUPPORTS_RISCV_ISA_ZBB systems that do not support the Zbb extension. endchoice + +config TOOLCHAIN_HAS_ZBC + bool + default y + depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zbc) + depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbc) + depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900 + depends on AS_HAS_OPTION_ARCH + +config RISCV_ISA_ZBC + bool + +choice + prompt "Zbc extension for bit manipulation instructions support" + default PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBC + help + This selects the level of support for Zbc instructions to be + built into the Linux Kernel. This does not impact whether Zbc + instructions are allowed to be emitted by user-space code. + + The Zbc extension provides instructions to accelerate carry-less + multiplication. + +config PROHIBIT_RISCV_ISA_ZBC + bool "Prohibit Zbc instruction sequences" + depends on NONPORTABLE + help + Regardless of if the platform supports Zbc instructions, + prohibit the kernel from emitting Zbc instructions. + +config PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBC + bool "Allow Zbc instruction sequences if supported" + depends on TOOLCHAIN_HAS_ZBC + depends on RISCV_ALTERNATIVE + select RISCV_ISA_ZBC + help + Add support for enabling optimisations in the kernel when the + Zbc extension is detected at boot. + +config PLATFORM_SUPPORTS_RISCV_ISA_ZBC + bool "Emit Zbc instructions when building Linux" + depends on TOOLCHAIN_HAS_ZBC + depends on NONPORTABLE + select RISCV_ISA_ZBC + help + Adds "zbc" to the ISA subsets that the toolchain is allowed to emit + when building Linux, which results in Zbc instructions in the + Linux binary. This option produces a kernel that will not run on + systems that do not support the Zbc extension. + +endchoice diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index c8ec38b9880a..57457d15e9a4 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -68,6 +68,7 @@ riscv-march-$(CONFIG_FPU) := $(riscv-march-y)fd riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_C) := $(riscv-march-y)c riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBA) := $(riscv-march-y)_zba riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBB) := $(riscv-march-y)_zbb +riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBC) := $(riscv-march-y)_zbc ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC KBUILD_CFLAGS += -Wa,-misa-spec=2.2 -- 2.44.0
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