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Message-Id: <20240507-compile_kernel_with_extensions-v2-8-722c21c328c6@rivosinc.com> Date: Tue, 07 May 2024 18:36:34 -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 8/8] riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBS Kconfig option Zbs can optimize kernel instruction sequences. Add a config option PLATFORM_SUPPORTS_RISCV_ISA_ZBS that allows arbitrary Zbs instruction sequences to be emitted by the compiler. The existing "RISCV_ISA_ZBS" option is repurposed to be used to by kernel code to determine if either PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBS or PLATFORM_SUPPORTS_RISCV_ISA_ZBS 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 b7399f236bba..60ae1bf71c70 100644 --- a/arch/riscv/Kconfig.isa +++ b/arch/riscv/Kconfig.isa @@ -340,3 +340,54 @@ config PLATFORM_SUPPORTS_RISCV_ISA_ZBC systems that do not support the Zbc extension. endchoice + +config TOOLCHAIN_HAS_ZBS + bool + default y + depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zbs) + depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbs) + depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900 + depends on AS_HAS_OPTION_ARCH + +config RISCV_ISA_ZBS + bool + +choice + prompt "Zbs extension for bit manipulation instructions support" + default PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBS + help + This selects the level of support for Zbs instructions to be + built into the Linux Kernel. This does not impact whether Zbs + instructions are allowed to be emitted by user-space code. + + The Zbs extension provides instructions to accelerate carry-less + multiplication. + +config PROHIBIT_RISCV_ISA_ZBS + bool "Prohibit Zbs instruction sequences" + depends on NONPORTABLE + help + Regardless of if the platform supports Zbs instructions, + prohibit the kernel from emitting Zbs instructions. + +config PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBS + bool "Allow Zbs instruction sequences if supported" + depends on TOOLCHAIN_HAS_ZBS + depends on RISCV_ALTERNATIVE + select RISCV_ISA_ZBS + help + Add support for enabling optimisations in the kernel when the + Zbs extension is detected at boot. + +config PLATFORM_SUPPORTS_RISCV_ISA_ZBS + bool "Emit Zbs instructions when building Linux" + depends on TOOLCHAIN_HAS_ZBS + depends on NONPORTABLE + select RISCV_ISA_ZBS + help + Adds "zbs" to the ISA subsets that the toolchain is allowed to emit + when building Linux, which results in Zbs instructions in the + Linux binary. This option produces a kernel that will not run on + systems that do not support the Zbs extension. + +endchoice diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index 57457d15e9a4..80ff8503196a 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -69,6 +69,7 @@ riscv-march-$(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) := $(riscv-march-y)_zbc +riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBS) := $(riscv-march-y)_zbs ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC KBUILD_CFLAGS += -Wa,-misa-spec=2.2 -- 2.44.0
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