linux-kernel - [v1 PATCH 2/2] RISC-V: Consolidate isa correctness check

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Date:   Thu,  3 Oct 2019 18:20:00 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexandre Ghiti <aghiti@...em.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anup Patel <anup@...infault.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        linux-riscv@...ts.infradead.org,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Richard Fontana <rfontana@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [v1 PATCH  2/2] RISC-V: Consolidate isa correctness check

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@....com>
---
 arch/riscv/include/asm/processor.h |  1 +
 arch/riscv/kernel/cpu.c            | 40 ++++++++++++++++++++++--------
 arch/riscv/kernel/cpufeature.c     |  4 +--
 arch/riscv/kernel/smpboot.c        |  4 +++
 4 files changed, 36 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..95ef5c91823d 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -8,13 +8,42 @@
 #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 defined(CONFIG_32BIT)
+	if (strncmp(*isa, "rv32i", 5) != 0)
+		return -ENODEV;
+#elif defined(CONFIG_64BIT)
+	if (strncmp(*isa, "rv64i", 5) != 0)
+		return -ENODEV;
+#endif
+
+	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 +61,6 @@ 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