[PATCH v3 7/7] RISC-V: always report presence of extensions formerly part of the base ISA

Conor Dooley
2023-06-07T20:29:22Z

Of these four extensions, two were part of the base ISA when the port was
written and are required by the kernel. The other two are implied when
`i` is in riscv,isa on DT systems.
There's not much that userspace can do with this extra information, but
there is no harm in reporting an ISA string that closer resembles the
current versions of the specifications either.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
Intentionally avoided your conditional tag here Drew.
---
arch/riscv/include/asm/hwcap.h | 4 ++++
arch/riscv/kernel/cpu.c | 4 ++++
arch/riscv/kernel/cpufeature.c | 17 +++++++++++++++++
3 files changed, 25 insertions(+)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index e0c40a4c63d5..e0eb9ad06805 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -46,6 +46,10 @@
#define RISCV_ISA_EXT_ZICBOZ 34
#define RISCV_ISA_EXT_SMAIA 35
#define RISCV_ISA_EXT_SSAIA 36
+#define RISCV_ISA_EXT_ZICNTR 37
+#define RISCV_ISA_EXT_ZICSR 38
+#define RISCV_ISA_EXT_ZIFENCEI 39
+#define RISCV_ISA_EXT_ZIHPM 40

#define RISCV_ISA_EXT_MAX 64
#define RISCV_ISA_EXT_NAME_LEN_MAX 32
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index dfb4a2a61050..6aea6412cf65 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -208,7 +208,11 @@ arch_initcall(riscv_cpuinfo_init);
static struct riscv_isa_ext_data isa_ext_arr[] = {
__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
__RISCV_ISA_EXT_DATA(zicboz, RISCV_ISA_EXT_ZICBOZ),
+ __RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
+ __RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),
+ __RISCV_ISA_EXT_DATA(zifencei, RISCV_ISA_EXT_ZIFENCEI),
__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
+ __RISCV_ISA_EXT_DATA(zihpm, RISCV_ISA_EXT_ZIHPM),
__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
__RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 84dc44a3e6e5..d21f7e8a33ef 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -311,6 +311,23 @@ void __init riscv_fill_hwcap(void)
#undef SET_ISA_EXT_MAP
}

+ /*
+ * Linux requires the following extensions, so we may as well
+ * always set them.
+ */
+ set_bit(RISCV_ISA_EXT_ZICSR, this_isa);
+ set_bit(RISCV_ISA_EXT_ZIFENCEI, this_isa);
+
+ /*
+ * These ones were as they were part of the base ISA when the
+ * port & dt-bindings were upstreamed, and so can be set
+ * unconditionally where `i` is in riscv,isa on DT systems.
+ */
+ if (acpi_disabled) {
+ set_bit(RISCV_ISA_EXT_ZICNTR, this_isa);
+ set_bit(RISCV_ISA_EXT_ZIHPM, this_isa);
+ }
+
/*
* All "okay" hart should have same isa. Set HWCAP based on
* common capabilities of every "okay" hart, in case they don't
--
2.39.2