[PATCH] LoongArch: Add debugfs entries to switch SFB/TSO state

From: Huacai Chen
Date: Thu Jan 09 2025 - 01:31:31 EST

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@xxxxxxxxxxx>
---
arch/loongarch/include/asm/loongarch.h | 15 +++
arch/loongarch/kernel/Makefile | 2 +-
arch/loongarch/kernel/kdebugfs.c | 168 +++++++++++++++++++++++++
arch/loongarch/kernel/unaligned.c | 8 +-
4 files changed, 186 insertions(+), 7 deletions(-)
create mode 100644 arch/loongarch/kernel/kdebugfs.c

diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index a3cc4f8d4c4a..15c245636176 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/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)
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 9497968ee158..4853e8b04c6f 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/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
diff --git a/arch/loongarch/kernel/kdebugfs.c b/arch/loongarch/kernel/kdebugfs.c
new file mode 100644
index 000000000000..cf1d89888e32
--- /dev/null
+++ b/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_IWUGO,
+ 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_IWUGO,
+ 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);
diff --git a/arch/loongarch/kernel/unaligned.c b/arch/loongarch/kernel/unaligned.c
index 3abf163dda05..487be604b96a 100644
--- a/arch/loongarch/kernel/unaligned.c
+++ b/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;
}
--
2.43.5