[PATCH v2 2/2] RISC-V: Consolidate isa correctness check

[Atish Patra]

Currently, isa string is read and checked for correctness at multiple
places.

Consolidate them into one function and use it only during early bootup.
In case of a incorrect isa string, the cpu shouldn't boot at all.

Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
---
 arch/riscv/include/asm/processor.h |  1 +
 arch/riscv/kernel/cpu.c            | 41 ++++++++++++++++++++++--------
 arch/riscv/kernel/cpufeature.c     |  4 +--
 arch/riscv/kernel/smpboot.c        |  4 +++
 4 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index f539149d04c2..189bf98f9a3f 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -74,6 +74,7 @@ static inline void wait_for_interrupt(void)
 }
 
 struct device_node;
+int riscv_read_check_isa(struct device_node *node, const char **isa);
 int riscv_of_processor_hartid(struct device_node *node);
 
 extern void riscv_fill_hwcap(void);
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 40a3c442ac5f..6bd4c7176bf6 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -8,13 +8,43 @@
 #include <linux/of.h>
 #include <asm/smp.h>
 
+int riscv_read_check_isa(struct device_node *node, const char **isa)
+{
+	u32 hart;
+
+	if (of_property_read_u32(node, "reg", &hart)) {
+		pr_warn("Found CPU without hart ID\n");
+		return -ENODEV;
+	}
+
+	if (of_property_read_string(node, "riscv,isa", isa)) {
+		pr_warn("CPU with hartid=%d has no \"riscv,isa\" property\n",
+			hart);
+		return -ENODEV;
+	}
+	/*
+	 * Linux doesn't support rv32e or rv128i, and we only support booting
+	 * kernels on harts with the same ISA that the kernel is compiled for.
+	 */
+	if (IS_ENABLED(CONFIG_32BIT) && (strncmp(*isa, "rv32i", 5) != 0)) {
+		pr_warn("hartid=%d has an invalid ISA \"%s\" for 32bit config\n",
+			hart, *isa);
+		return -ENODEV;
+	} else if (IS_ENABLED(CONFIG_64BIT) &&
+		  (strncmp(*isa, "rv64i", 5) != 0)) {
+		pr_warn("hartid=%d has an invalid ISA \"%s\" for 64bit config\n",
+			hart, *isa);
+		return -ENODEV;
+	}
+	return 0;
+}
+
 /*
  * Returns the hart ID of the given device tree node, or -ENODEV if the node
  * isn't an enabled and valid RISC-V hart node.
  */
 int riscv_of_processor_hartid(struct device_node *node)
 {
-	const char *isa;
 	u32 hart;
 
 	if (!of_device_is_compatible(node, "riscv")) {
@@ -32,15 +62,6 @@ int riscv_of_processor_hartid(struct device_node *node)
 		return -ENODEV;
 	}
 
-	if (of_property_read_string(node, "riscv,isa", &isa)) {
-		pr_warn("CPU with hartid=%d has no \"riscv,isa\" property\n", hart);
-		return -ENODEV;
-	}
-	if (isa[0] != 'r' || isa[1] != 'v') {
-		pr_warn("CPU with hartid=%d has an invalid ISA of \"%s\"\n", hart, isa);
-		return -ENODEV;
-	}
-
 	return hart;
 }
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index b1ade9a49347..eaad5aa07403 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -38,10 +38,8 @@ void riscv_fill_hwcap(void)
 		if (riscv_of_processor_hartid(node) < 0)
 			continue;
 
-		if (of_property_read_string(node, "riscv,isa", &isa)) {
-			pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
+		if (riscv_read_check_isa(node, &isa) < 0)
 			continue;
-		}
 
 		for (i = 0; i < strlen(isa); ++i)
 			this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 18ae6da5115e..15ee71297abf 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -60,12 +60,16 @@ void __init setup_smp(void)
 	int hart;
 	bool found_boot_cpu = false;
 	int cpuid = 1;
+	const char *isa;
 
 	for_each_of_cpu_node(dn) {
 		hart = riscv_of_processor_hartid(dn);
 		if (hart < 0)
 			continue;
 
+		if (riscv_read_check_isa(dn, &isa) < 0)
+			continue;
+
 		if (hart == cpuid_to_hartid_map(0)) {
 			BUG_ON(found_boot_cpu);
 			found_boot_cpu = 1;
-- 
2.21.0