Merge patch series "riscv: Extension parsing fixes"

Charlie Jenkins <charlie@rivosinc.com> says:

This series contains two minor fixes for the extension parsing in
cpufeature.c.

Some T-Head boards without vector 1.0 support report "v" in the isa
string in their DT which will cause the kernel to run vector code. The
code to blacklist "v" from these boards was doing so by using
riscv_cached_mvendorid() which has not been populated at the time of
extension parsing. This fix instead greedily reads the mvendorid CSR of
the boot hart to determine if the cpu is from T-Head.

The other fix is for an incorrect indexing bug. riscv extensions
sometimes imply other extensions. When adding these "subset" extensions
to the hardware capabilities array, they need to be checked if they are
valid. The current code only checks if the extension that is including
other extensions is valid and not the subset extensions.

These patches were previously included in:
https://lore.kernel.org/lkml/20240420-dev-charlie-support_thead_vector_6_9-v3-0-67cff4271d1d@rivosinc.com/

* b4-shazam-merge:
  riscv: cpufeature: Fix extension subset checking
  riscv: cpufeature: Fix thead vector hwcap removal

Link: https://lore.kernel.org/r/20240502-cpufeature_fixes-v4-0-b3d1a088722d@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

2 files changed, 43 insertions, 7 deletions

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..5ef48cb20ee1 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;
@@ -544,8 +549,7 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
 		 * CPU cores with the ratified spec will contain non-zero
 		 * marchid.
 		 */
-		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);
 		}
@@ -599,7 +603,7 @@ static int __init riscv_fill_hwcap_from_ext_list(unsigned long *isa2hwcap)
 
 			if (ext->subset_ext_size) {
 				for (int j = 0; j < ext->subset_ext_size; j++) {
-					if (riscv_isa_extension_check(ext->subset_ext_ids[i]))
+					if (riscv_isa_extension_check(ext->subset_ext_ids[j]))
 						set_bit(ext->subset_ext_ids[j], isainfo->isa);
 				}
 			}