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Message-Id: <20240506-compile_kernel_with_extensions-v1-6-5c25c134c097@rivosinc.com>
Date: Mon, 06 May 2024 18:40:47 -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>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 6/8] riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBA Kconfig
option
Zba can optimize kernel instruction sequences. Add a config option
PLATFORM_SUPPORTS_RISCV_ISA_ZBA that allows arbitrary Zba instruction
sequences to be emitted by the compiler.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
arch/riscv/Kconfig.isa | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
arch/riscv/Makefile | 1 +
2 files changed, 53 insertions(+)
diff --git a/arch/riscv/Kconfig.isa b/arch/riscv/Kconfig.isa
index 49bed8c75263..e7f28dc44137 100644
--- a/arch/riscv/Kconfig.isa
+++ b/arch/riscv/Kconfig.isa
@@ -186,6 +186,58 @@ config PLATFORM_MAY_SUPPORT_RISCV_ISA_SVPBMT
If you don't know what to do here, say Y.
+
+config TOOLCHAIN_HAS_ZBA
+ bool
+ default y
+ depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zba)
+ depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zba)
+ depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
+ depends on AS_HAS_OPTION_ARCH
+
+config RISCV_ISA_ZBA
+ bool
+
+choice
+ prompt "Zba extension for address generation instructions support"
+ default PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBA
+ help
+ This selects the level of support for Zba instructions to be
+ built into the Linux Kernel. This does not impact whether Zba
+ instructions are allowed to be emitted by user-space code.
+
+ The Zba extension provides instructions to accelerate a number
+ of address generation instruction sequences.
+
+config PROHIBIT_RISCV_ISA_ZBA
+ bool "Prohibit Zba instruction sequences"
+ depends on NONPORTABLE
+ help
+ Regardless of if the platform supports Zba instructions,
+ prohibit the kernel from emitting Zba instructions.
+
+config PLATFORM_MAY_SUPPORT_RISCV_ISA_ZBA
+ bool "Allow Zba instruction sequences if supported"
+ depends on TOOLCHAIN_HAS_ZBB
+ depends on RISCV_ALTERNATIVE
+ select RISCV_ISA_ZBA
+ help
+ Add support for enabling optimisations in the kernel when the
+ Zba extension is detected at boot.
+
+config PLATFORM_SUPPORTS_RISCV_ISA_ZBA
+ bool "Emit Zba instructions when building Linux"
+ depends on TOOLCHAIN_HAS_ZBB
+ depends on NONPORTABLE
+ select RISCV_ISA_ZBA
+ help
+ Adds "zba" to the ISA subsets that the toolchain is allowed to emit
+ when building Linux, which results in Zba instructions in the
+ Linux binary. This option produces a kernel that will not run on
+ systems that do not support the Zba extension.
+
+endchoice
+
config TOOLCHAIN_HAS_ZBB
bool
default y
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 934e20de576b..0ab4cc5dfffb 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -67,6 +67,7 @@ riscv-march-$(CONFIG_ARCH_RV64I) := rv64ima
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_V) := $(riscv-march-y)v
+riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBA) := $(riscv-march-y)_zba
riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_ZBB) := $(riscv-march-y)_zbb
ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
--
2.44.0
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