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

[Charlie Jenkins]

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 at 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