1 files changed, 73 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpuid/leaf_0x2_api.h b/arch/x86/include/asm/cpuid/leaf_0x2_api.h
new file mode 100644
index 000000000000..09fa3070b271
--- /dev/null
+++ b/arch/x86/include/asm/cpuid/leaf_0x2_api.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_CPUID_LEAF_0x2_API_H
+#define _ASM_X86_CPUID_LEAF_0x2_API_H
+
+#include <asm/cpuid/api.h>
+#include <asm/cpuid/types.h>
+
+/**
+ * cpuid_get_leaf_0x2_regs() - Return sanitized leaf 0x2 register output
+ * @regs:	Output parameter
+ *
+ * Query CPUID leaf 0x2 and store its output in @regs.	Force set any
+ * invalid 1-byte descriptor returned by the hardware to zero (the NULL
+ * cache/TLB descriptor) before returning it to the caller.
+ *
+ * Use for_each_leaf_0x2_entry() to iterate over the register output in
+ * parsed form.
+ */
+static inline void cpuid_get_leaf_0x2_regs(union leaf_0x2_regs *regs)
+{
+	cpuid_leaf(0x2, regs);
+
+	/*
+	 * All Intel CPUs must report an iteration count of 1.	In case
+	 * of bogus hardware, treat all returned descriptors as NULL.
+	 */
+	if (regs->desc[0] != 0x01) {
+		for (int i = 0; i < 4; i++)
+			regs->regv[i] = 0;
+		return;
+	}
+
+	/*
+	 * The most significant bit (MSB) of each register must be clear.
+	 * If a register is invalid, replace its descriptors with NULL.
+	 */
+	for (int i = 0; i < 4; i++) {
+		if (regs->reg[i].invalid)
+			regs->regv[i] = 0;
+	}
+}
+
+/**
+ * for_each_leaf_0x2_entry() - Iterator for parsed leaf 0x2 descriptors
+ * @regs:   Leaf 0x2 register output, returned by cpuid_get_leaf_0x2_regs()
+ * @__ptr:  u8 pointer, for macro internal use only
+ * @entry:  Pointer to parsed descriptor information at each iteration
+ *
+ * Loop over the 1-byte descriptors in the passed leaf 0x2 output registers
+ * @regs.  Provide the parsed information for each descriptor through @entry.
+ *
+ * To handle cache-specific descriptors, switch on @entry->c_type.  For TLB
+ * descriptors, switch on @entry->t_type.
+ *
+ * Example usage for cache descriptors::
+ *
+ *	const struct leaf_0x2_table *entry;
+ *	union leaf_0x2_regs regs;
+ *	u8 *ptr;
+ *
+ *	cpuid_get_leaf_0x2_regs(&regs);
+ *	for_each_leaf_0x2_entry(regs, ptr, entry) {
+ *		switch (entry->c_type) {
+ *			...
+ *		}
+ *	}
+ */
+#define for_each_leaf_0x2_entry(regs, __ptr, entry)				\
+	for (__ptr = &(regs).desc[1];						\
+	     __ptr < &(regs).desc[16] && (entry = &cpuid_0x2_table[*__ptr]);	\
+	     __ptr++)
+
+#endif /* _ASM_X86_CPUID_LEAF_0x2_API_H */