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Message-Id: <20240506-compile_kernel_with_extensions-v1-1-5c25c134c097@rivosinc.com>
Date: Mon, 06 May 2024 18:40:42 -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 1/8] riscv: Add PLATFORM_MAY_SUPPORT_RISCV_ISA_C Kconfig
option
Introduce a "Kernel ISA" menu and migrate the compressed instruction
support options into a new file Kconfig.isa. Add a new option
"PLATFORM_MAY_SUPPORT_RISCV_ISA_C" that can be used to conditionally
emit C extensions if the hardware supports it.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
arch/riscv/Kconfig | 19 +++++++-----------
arch/riscv/Kconfig.isa | 41 ++++++++++++++++++++++++++++++++++++++
arch/riscv/Makefile | 4 ++--
arch/riscv/kernel/probes/uprobes.c | 2 +-
arch/riscv/net/bpf_jit.h | 4 +++-
5 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c8bdfd33abf4..c2a4f5364707 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -369,6 +369,12 @@ config ARCH_RV64I
endchoice
+menu "Kernel ISA"
+
+source "arch/riscv/Kconfig.isa"
+
+endmenu
+
# We must be able to map all physical memory into the kernel, but the compiler
# is still a bit more efficient when generating code if it's setup in a manner
# such that it can only map 2GiB of memory.
@@ -478,17 +484,6 @@ config RISCV_ALTERNATIVE_EARLY
help
Allows early patching of the kernel for special errata
-config RISCV_ISA_C
- bool "Emit compressed instructions when building Linux"
- default y
- help
- Adds "C" to the ISA subsets that the toolchain is allowed to emit
- when building Linux, which results in compressed instructions in the
- Linux binary. This option produces a kernel that will not run on
- systems that do not support compressed instructions.
-
- If you don't know what to do here, say Y.
-
config RISCV_ISA_SVNAPOT
bool "Svnapot extension support for supervisor mode NAPOT pages"
depends on 64BIT && MMU
@@ -937,6 +932,7 @@ config EFI
bool "UEFI runtime support"
depends on OF && !XIP_KERNEL
depends on MMU
+ depends on PLATFORM_SUPPORTS_RISCV_ISA_C
default y
select ARCH_SUPPORTS_ACPI if 64BIT
select EFI_GENERIC_STUB
@@ -944,7 +940,6 @@ config EFI
select EFI_RUNTIME_WRAPPERS
select EFI_STUB
select LIBFDT
- select RISCV_ISA_C
select UCS2_STRING
help
This option provides support for runtime services provided
diff --git a/arch/riscv/Kconfig.isa b/arch/riscv/Kconfig.isa
new file mode 100644
index 000000000000..08b7af5aabb0
--- /dev/null
+++ b/arch/riscv/Kconfig.isa
@@ -0,0 +1,41 @@
+config RISCV_ISA_C
+ bool
+
+choice
+ prompt "Compressed instruction support"
+ default PLATFORM_SUPPORTS_RISCV_ISA_C
+ help
+ This selects the level of support for compressed instructions to be
+ built into the Linux Kernel. This does not impact whether compressed
+ instructions are allowed to be emitted by user-space code.
+
+config PROHIBIT_RISCV_ISA_C
+ bool "Prohibit compressed instructions"
+ depends on NONPORTABLE
+ help
+ Regardless of if the platform supports compressed instructions,
+ prohibit the kernel from emitting compressed instructions.
+
+config PLATFORM_MAY_SUPPORT_RISCV_ISA_C
+ bool "Allow compressed instructions sequences if supported"
+ depends on FPU
+ depends on NONPORTABLE
+ select RISCV_ISA_C
+ help
+ Only allow compressed instructions to be emitted if "C" is present in
+ the device tree or ACPI table. No compressed instructions will be
+ emitted if the platform does not support them.
+
+config PLATFORM_SUPPORTS_RISCV_ISA_C
+ bool "Emit compressed instructions when building Linux"
+ depends on FPU
+ select RISCV_ISA_C
+ help
+ Adds "C" to the ISA subsets that the toolchain is allowed to emit
+ when building Linux, which results in compressed instructions in the
+ Linux binary. This option produces a kernel that will not run on
+ systems that do not support compressed instructions.
+
+ If you don't know what to do here, say Y.
+
+endchoice
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 5b3115a19852..e1be36004097 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -14,7 +14,7 @@ endif
ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
LDFLAGS_vmlinux += --no-relax
KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
-ifeq ($(CONFIG_RISCV_ISA_C),y)
+ifeq ($(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_C),y)
CC_FLAGS_FTRACE := -fpatchable-function-entry=4
else
CC_FLAGS_FTRACE := -fpatchable-function-entry=2
@@ -65,7 +65,7 @@ endif
riscv-march-$(CONFIG_ARCH_RV32I) := rv32ima
riscv-march-$(CONFIG_ARCH_RV64I) := rv64ima
riscv-march-$(CONFIG_FPU) := $(riscv-march-y)fd
-riscv-march-$(CONFIG_RISCV_ISA_C) := $(riscv-march-y)c
+riscv-march-$(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_C) := $(riscv-march-y)c
riscv-march-$(CONFIG_RISCV_ISA_V) := $(riscv-march-y)v
ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index 4b3dc8beaf77..a468689a6f6d 100644
--- a/arch/riscv/kernel/probes/uprobes.c
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -11,7 +11,7 @@
bool is_swbp_insn(uprobe_opcode_t *insn)
{
-#ifdef CONFIG_RISCV_ISA_C
+#ifdef CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_C
return (*insn & 0xffff) == UPROBE_SWBP_INSN;
#else
return *insn == UPROBE_SWBP_INSN;
diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
index f4b6b3b9edda..259294bdbc3a 100644
--- a/arch/riscv/net/bpf_jit.h
+++ b/arch/riscv/net/bpf_jit.h
@@ -15,7 +15,9 @@
static inline bool rvc_enabled(void)
{
- return IS_ENABLED(CONFIG_RISCV_ISA_C);
+ return IS_ENABLED(CONFIG_PLATFORM_SUPPORTS_RISCV_ISA_C) ||
+ (IS_ENABLED(CONFIG_PLATFORM_MAY_SUPPORT_RISCV_ISA_C) &&
+ riscv_has_extension_likely(RISCV_ISA_EXT_c));
}
static inline bool rvzbb_enabled(void)
--
2.44.0
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