LoongArch: Add debugfs entries to switch SFB/TSO state

We need to switch SFB (Store Fill Buffer) and TSO (Total Store Order)
state at runtime to debug memory management and KVM virtualization, so
add two debugfs entries "sfb_state" and "tso_state" under the directory
/sys/kernel/debug/loongarch.

Query SFB:
cat /sys/kernel/debug/loongarch/sfb_state

Enable SFB:
echo 1 > /sys/kernel/debug/loongarch/sfb_state

Disable SFB:
echo 0 > /sys/kernel/debug/loongarch/sfb_state

Query TSO:
cat /sys/kernel/debug/loongarch/tso_state

Switch TSO:
echo [TSO] > /sys/kernel/debug/loongarch/tso_state

Available [TSO] states:
0 (No Load No Store)    1 (All Load No Store)   3 (Same Load No Store)
4 (No Load All Store)   5 (All Load All Store)  7 (Same Load All Store)

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/loongarch.h

@@ -108,6 +108,12 @@
 #define  CPUCFG3_SPW_HG_HF		BIT(11)
 #define  CPUCFG3_RVA			BIT(12)
 #define  CPUCFG3_RVAMAX			GENMASK(16, 13)
+#define  CPUCFG3_ALDORDER_CAP		BIT(18) /* All address load ordered, capability */
+#define  CPUCFG3_ASTORDER_CAP		BIT(19) /* All address store ordered, capability */
+#define  CPUCFG3_ALDORDER_STA		BIT(20) /* All address load ordered, status */
+#define  CPUCFG3_ASTORDER_STA		BIT(21) /* All address store ordered, status */
+#define  CPUCFG3_SLDORDER_CAP		BIT(22) /* Same address load ordered, capability */
+#define  CPUCFG3_SLDORDER_STA		BIT(23) /* Same address load ordered, status */
 
 #define LOONGARCH_CPUCFG4		0x4
 #define  CPUCFG4_CCFREQ			GENMASK(31, 0)
@@ -565,6 +571,15 @@
 
 /* Implement dependent */
 #define LOONGARCH_CSR_IMPCTL1		0x80	/* Loongson config1 */
+#define  CSR_LDSTORDER_SHIFT		28
+#define  CSR_LDSTORDER_WIDTH		3
+#define  CSR_LDSTORDER_MASK		(_ULCAST_(0x7) << CSR_LDSTORDER_SHIFT)
+#define  CSR_LDSTORDER_NLD_NST		(_ULCAST_(0x0) << CSR_LDSTORDER_SHIFT) /* 000 = No Load No Store */
+#define  CSR_LDSTORDER_ALD_NST		(_ULCAST_(0x1) << CSR_LDSTORDER_SHIFT) /* 001 = All Load No Store */
+#define  CSR_LDSTORDER_SLD_NST		(_ULCAST_(0x3) << CSR_LDSTORDER_SHIFT) /* 011 = Same Load No Store */
+#define  CSR_LDSTORDER_NLD_AST		(_ULCAST_(0x4) << CSR_LDSTORDER_SHIFT) /* 100 = No Load All Store */
+#define  CSR_LDSTORDER_ALD_AST		(_ULCAST_(0x5) << CSR_LDSTORDER_SHIFT) /* 101 = All Load All Store */
+#define  CSR_LDSTORDER_SLD_AST		(_ULCAST_(0x7) << CSR_LDSTORDER_SHIFT) /* 111 = Same Load All Store */
 #define  CSR_MISPEC_SHIFT		20
 #define  CSR_MISPEC_WIDTH		8
 #define  CSR_MISPEC			(_ULCAST_(0xff) << CSR_MISPEC_SHIFT)

arch/loongarch/kernel/Makefile

@@ -10,7 +10,7 @@ extra-y		:= vmlinux.lds
 obj-y		+= head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
 		   traps.o irq.o idle.o process.o dma.o mem.o reset.o switch.o \
 		   elf.o syscall.o signal.o time.o topology.o inst.o ptrace.o vdso.o \
-		   alternative.o unwind.o
+		   alternative.o kdebugfs.o unwind.o
 
 obj-$(CONFIG_ACPI)		+= acpi.o
 obj-$(CONFIG_EFI) 		+= efi.o

arch/loongarch/kernel/kdebugfs.c

@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/debugfs.h>
+#include <linux/kstrtox.h>
+#include <asm/loongarch.h>
+
+struct dentry *arch_debugfs_dir;
+EXPORT_SYMBOL(arch_debugfs_dir);
+
+static int sfb_state, tso_state;
+
+static void set_sfb_state(void *info)
+{
+	int val = *(int *)info << CSR_STFILL_SHIFT;
+
+	csr_xchg32(val, CSR_STFILL, LOONGARCH_CSR_IMPCTL1);
+}
+
+static ssize_t sfb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	int s, state;
+	char str[32];
+
+	state = (csr_read32(LOONGARCH_CSR_IMPCTL1) & CSR_STFILL) >> CSR_STFILL_SHIFT;
+
+	s = snprintf(str, sizeof(str), "Boot State: %x\nCurrent State: %x\n", sfb_state, state);
+
+	if (*ppos >= s)
+		return 0;
+
+	s -= *ppos;
+	s = min_t(u32, s, count);
+
+	if (copy_to_user(buf, &str[*ppos], s))
+		return -EFAULT;
+
+	*ppos += s;
+
+	return s;
+}
+
+static ssize_t sfb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+	int state;
+
+	if (kstrtoint_from_user(buf, count, 10, &state))
+		return -EFAULT;
+
+	switch (state) {
+	case 0: case 1:
+		on_each_cpu(set_sfb_state, &state, 1);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static const struct file_operations sfb_fops = {
+	.read = sfb_read,
+	.write = sfb_write,
+	.open = simple_open,
+	.llseek = default_llseek
+};
+
+#define LDSTORDER_NLD_NST        0x0 /* 000 = No Load No Store */
+#define LDSTORDER_ALD_NST        0x1 /* 001 = All Load No Store */
+#define LDSTORDER_SLD_NST        0x3 /* 011 = Same Load No Store */
+#define LDSTORDER_NLD_AST        0x4 /* 100 = No Load All Store */
+#define LDSTORDER_ALD_AST        0x5 /* 101 = All Load All Store */
+#define LDSTORDER_SLD_AST        0x7 /* 111 = Same Load All Store */
+
+static char *tso_hints[] = {
+	"No Load No Store",
+	"All Load No Store",
+	"Invalid Config",
+	"Same Load No Store",
+	"No Load All Store",
+	"All Load All Store",
+	"Invalid Config",
+	"Same Load All Store"
+};
+
+static void set_tso_state(void *info)
+{
+	int val = *(int *)info << CSR_LDSTORDER_SHIFT;
+
+	csr_xchg32(val, CSR_LDSTORDER_MASK, LOONGARCH_CSR_IMPCTL1);
+}
+
+static ssize_t tso_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	int s, state;
+	char str[240];
+
+	state = (csr_read32(LOONGARCH_CSR_IMPCTL1) & CSR_LDSTORDER_MASK) >> CSR_LDSTORDER_SHIFT;
+
+	s = snprintf(str, sizeof(str), "Boot State: %d (%s)\n"
+			               "Current State: %d (%s)\n\n"
+				       "Available States:\n"
+				       "0 (%s)\t" "1 (%s)\t" "3 (%s)\n"
+				       "4 (%s)\t" "5 (%s)\t" "7 (%s)\n",
+				       tso_state, tso_hints[tso_state], state, tso_hints[state],
+				       tso_hints[0], tso_hints[1], tso_hints[3], tso_hints[4], tso_hints[5], tso_hints[7]);
+
+	if (*ppos >= s)
+		return 0;
+
+	s -= *ppos;
+	s = min_t(u32, s, count);
+
+	if (copy_to_user(buf, &str[*ppos], s))
+		return -EFAULT;
+
+	*ppos += s;
+
+	return s;
+}
+
+static ssize_t tso_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+	int state;
+
+	if (kstrtoint_from_user(buf, count, 10, &state))
+		return -EFAULT;
+
+	switch (state) {
+	case 0: case 1: case 3:
+	case 4: case 5: case 7:
+		on_each_cpu(set_tso_state, &state, 1);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static const struct file_operations tso_fops = {
+	.read = tso_read,
+	.write = tso_write,
+	.open = simple_open,
+	.llseek = default_llseek
+};
+
+static int __init arch_kdebugfs_init(void)
+{
+	unsigned int config = read_cpucfg(LOONGARCH_CPUCFG3);
+
+	arch_debugfs_dir = debugfs_create_dir("loongarch", NULL);
+
+	if (config & CPUCFG3_SFB) {
+		debugfs_create_file("sfb_state", S_IRUGO | S_IWUSR,
+			    arch_debugfs_dir, &sfb_state, &sfb_fops);
+		sfb_state = (csr_read32(LOONGARCH_CSR_IMPCTL1) & CSR_STFILL) >> CSR_STFILL_SHIFT;
+	}
+
+	if (config & (CPUCFG3_ALDORDER_CAP | CPUCFG3_ASTORDER_CAP)) {
+		debugfs_create_file("tso_state", S_IRUGO | S_IWUSR,
+			    arch_debugfs_dir, &tso_state, &tso_fops);
+		tso_state = (csr_read32(LOONGARCH_CSR_IMPCTL1) & CSR_LDSTORDER_MASK) >> CSR_LDSTORDER_SHIFT;
+	}
+
+	return 0;
+}
+postcore_initcall(arch_kdebugfs_init);

arch/loongarch/kernel/unaligned.c

@@ -482,14 +482,10 @@ void emulate_load_store_insn(struct pt_regs *regs, void __user *addr, unsigned i
 #ifdef CONFIG_DEBUG_FS
 static int __init debugfs_unaligned(void)
 {
-	struct dentry *d;
-
-	d = debugfs_create_dir("loongarch", NULL);
-
 	debugfs_create_u32("unaligned_instructions_user",
-				S_IRUGO, d, &unaligned_instructions_user);
+				S_IRUGO, arch_debugfs_dir, &unaligned_instructions_user);
 	debugfs_create_u32("unaligned_instructions_kernel",
-				S_IRUGO, d, &unaligned_instructions_kernel);
+				S_IRUGO, arch_debugfs_dir, &unaligned_instructions_kernel);
 
 	return 0;
 }