[PATCH v3 1/2] riscv: cpufeature: Fix thead vector hwcap removal

[Charlie Jenkins]

The riscv_cpuinfo struct that contains mvendorid and marchid is not
populated until all harts are booted which happens after the DT parsing.
Use the mvendorid/marchid from the boot hart to determine if the DT
contains an invalid V.

Fixes: d82f32202e0d ("RISC-V: Ignore V from the riscv,isa DT property on older T-Head CPUs")
Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
Reviewed-by: Guo Ren <guoren at kernel.org>
---
 arch/riscv/include/asm/sbi.h   |  2 ++
 arch/riscv/kernel/cpu.c        | 40 ++++++++++++++++++++++++++++++++++++----
 arch/riscv/kernel/cpufeature.c | 10 ++++++++--
 3 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 6e68f8dff76b..0fab508a65b3 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -370,6 +370,8 @@ static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1
 static inline void sbi_init(void) {}
 #endif /* CONFIG_RISCV_SBI */
 
+unsigned long riscv_get_mvendorid(void);
+unsigned long riscv_get_marchid(void);
 unsigned long riscv_cached_mvendorid(unsigned int cpu_id);
 unsigned long riscv_cached_marchid(unsigned int cpu_id);
 unsigned long riscv_cached_mimpid(unsigned int cpu_id);
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index d11d6320fb0d..c1f3655238fd 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -139,6 +139,34 @@ int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
 	return -1;
 }
 
+unsigned long __init riscv_get_marchid(void)
+{
+	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
+
+#if IS_ENABLED(CONFIG_RISCV_SBI)
+	ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
+#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
+	ci->marchid = csr_read(CSR_MARCHID);
+#else
+	ci->marchid = 0;
+#endif
+	return ci->marchid;
+}
+
+unsigned long __init riscv_get_mvendorid(void)
+{
+	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
+
+#if IS_ENABLED(CONFIG_RISCV_SBI)
+	ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
+#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
+	ci->mvendorid = csr_read(CSR_MVENDORID);
+#else
+	ci->mvendorid = 0;
+#endif
+	return ci->mvendorid;
+}
+
 DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 
 unsigned long riscv_cached_mvendorid(unsigned int cpu_id)
@@ -170,12 +198,16 @@ static int riscv_cpuinfo_starting(unsigned int cpu)
 	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
 
 #if IS_ENABLED(CONFIG_RISCV_SBI)
-	ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
-	ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
+	if (!ci->mvendorid)
+		ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
+	if (!ci->marchid)
+		ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
 	ci->mimpid = sbi_spec_is_0_1() ? 0 : sbi_get_mimpid();
 #elif IS_ENABLED(CONFIG_RISCV_M_MODE)
-	ci->mvendorid = csr_read(CSR_MVENDORID);
-	ci->marchid = csr_read(CSR_MARCHID);
+	if (!ci->mvendorid)
+		ci->mvendorid = csr_read(CSR_MVENDORID);
+	if (!ci->marchid)
+		ci->marchid = csr_read(CSR_MARCHID);
 	ci->mimpid = csr_read(CSR_MIMPID);
 #else
 	ci->mvendorid = 0;
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 3ed2359eae35..818adb0d388e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -490,6 +490,8 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
 	struct acpi_table_header *rhct;
 	acpi_status status;
 	unsigned int cpu;
+	u64 boot_vendorid;
+	u64 boot_archid;
 
 	if (!acpi_disabled) {
 		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
@@ -497,6 +499,9 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
 			return;
 	}
 
+	boot_vendorid = riscv_get_mvendorid();
+	boot_archid = riscv_get_marchid();
+
 	for_each_possible_cpu(cpu) {
 		struct riscv_isainfo *isainfo = &hart_isa[cpu];
 		unsigned long this_hwcap = 0;
@@ -543,9 +548,10 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
 		 * version of the vector specification put "v" into their DTs.
 		 * CPU cores with the ratified spec will contain non-zero
 		 * marchid.
+		 *
+		 * Disable vector if the boot hart has a T-Head mvendorid and an marchid of 0.
 		 */
-		if (acpi_disabled && riscv_cached_mvendorid(cpu) == THEAD_VENDOR_ID &&
-		    riscv_cached_marchid(cpu) == 0x0) {
+		if (acpi_disabled && boot_vendorid == THEAD_VENDOR_ID && boot_archid == 0x0) {
 			this_hwcap &= ~isa2hwcap[RISCV_ISA_EXT_v];
 			clear_bit(RISCV_ISA_EXT_v, isainfo->isa);
 		}

-- 
2.44.0