[PATCH RFC v7 1/3] riscv: Add RISC-V Svrsw60t59b extension support

[Deepak Gupta]

On Wed, Apr 09, 2025 at 05:53:18PM +0800, Chunyan Zhang wrote:
>The Svrsw60t59b extension allows to free the PTE reserved bits 60
>and 59 for software to use.
>
>Signed-off-by: Chunyan Zhang <zhangchunyan at iscas.ac.cn>
>---
> arch/riscv/Kconfig             | 13 +++++++++++++
> arch/riscv/include/asm/hwcap.h |  1 +
> arch/riscv/kernel/cpufeature.c |  1 +
> 3 files changed, 15 insertions(+)
>
>diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>index bbec87b79309..332fc00243ad 100644
>--- a/arch/riscv/Kconfig
>+++ b/arch/riscv/Kconfig
>@@ -842,6 +842,19 @@ config RISCV_ISA_ZICBOZ
>
> 	   If you don't know what to do here, say Y.
>
>+config RISCV_ISA_SVRSW60T59B
>+	bool "Svrsw60t59b extension support for using PTE bits 60 and 59"
>+	depends on RISCV_ALTERNATIVE

depends on MMU && 64BIT as well.

>+	default y
>+	help
>+	  Adds support to dynamically detect the presence of the SVRSW60T59B
>+	  extension and enable its usage.
>+
>+	  The Svrsw60t59b extension allows to free the PTE reserved bits 60
>+	  and 59 for software to use.
>+
>+	  If you don't know what to do here, say Y.
>+
> config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
> 	def_bool y
> 	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
>diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
>index e3cbf203cdde..985f6dfc80ed 100644
>--- a/arch/riscv/include/asm/hwcap.h
>+++ b/arch/riscv/include/asm/hwcap.h
>@@ -105,6 +105,7 @@
> #define RISCV_ISA_EXT_ZVFBFWMA		96
> #define RISCV_ISA_EXT_ZAAMO		97
> #define RISCV_ISA_EXT_ZALRSC		98
>+#define RISCV_ISA_EXT_SVRSW60T59B	99
>
> #define RISCV_ISA_EXT_XLINUXENVCFG	127
>
>diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>index 2054f6c4b0ae..0f0f3027d400 100644
>--- a/arch/riscv/kernel/cpufeature.c
>+++ b/arch/riscv/kernel/cpufeature.c
>@@ -523,6 +523,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
> 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
> 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> 	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),
>+	__RISCV_ISA_EXT_DATA(svrsw60t59b, RISCV_ISA_EXT_SVRSW60T59B),
> };
>
> const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext);
>-- 
>2.34.1
>