[PATCH 15/19] riscv: hwcap: Add v to hwcap if xtheadvector enabled

Charlie Jenkins
2024-04-12T04:15:07Z

xtheadvector is not vector 1.0 compatible, but it can leverage all of
the same save/restore routines as vector plus
riscv_v_first_use_handler(). vector 1.0 and xtheadvector are mutually
exclusive so there is no risk of overlap.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
arch/riscv/kernel/cpufeature.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 41a4d2028428..59f628b1341c 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -647,9 +647,13 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
* Many vendors with T-Head CPU cores which implement the 0.7.1
* version of the vector specification put "v" into their DTs.
* CPU cores with the ratified spec will contain non-zero
- * marchid.
+ * marchid. Only allow "v" to be set if xtheadvector is present.
*/
- if (acpi_disabled && this_vendorid == THEAD_VENDOR_ID &&
+ if (__riscv_isa_vendor_extension_available(isavendorinfo->isa,
+ RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+ this_hwcap |= isa2hwcap[RISCV_ISA_EXT_v];
+ set_bit(RISCV_ISA_EXT_v, isainfo->isa);
+ } else if (acpi_disabled && this_vendorid == THEAD_VENDOR_ID &&
this_archid == 0x0) {
this_hwcap &= ~isa2hwcap[RISCV_ISA_EXT_v];
clear_bit(RISCV_ISA_EXT_v, isainfo->isa);
@@ -776,6 +780,15 @@ static int __init riscv_fill_hwcap_from_ext_list(unsigned long *isa2hwcap)

of_node_put(cpu_node);

+ /*
+ * Enable kernel vector routines if xtheadvector is present
+ */
+ if (__riscv_isa_vendor_extension_available(isavendorinfo->isa,
+ RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+ this_hwcap |= isa2hwcap[RISCV_ISA_EXT_v];
+ set_bit(RISCV_ISA_EXT_v, isainfo->isa);
+ }
+
/*
* All "okay" harts should have same isa. Set HWCAP based on
* common capabilities of every "okay" hart, in case they don't.

--
2.44.0