[patch v2 20/38] x86/cpu: Provide cpuid_read() et al.

[Thomas Gleixner <tglx@linutronix.de>]

Provide a few helper functions to read CPUID leafs or individual registers
into a data structure without requiring unions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/cpuid.h |   32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

--- a/arch/x86/include/asm/cpuid.h
+++ b/arch/x86/include/asm/cpuid.h
@@ -127,6 +127,38 @@ static inline unsigned int cpuid_edx(uns
 	return edx;
 }
 
+static inline void __cpuid_read(unsigned int leaf, unsigned int subleaf, u32 *regs)
+{
+	regs[CPUID_EAX] = leaf;
+	regs[CPUID_ECX] = subleaf;
+	__cpuid(regs, regs + 1, regs + 2, regs + 3);
+}
+
+#define cpuid_subleaf(leaf, subleaf, regs)		\
+	BUILD_BUG_ON(sizeof(*(regs)) != 16);		\
+	__cpuid_read(leaf, subleaf, (u32 *)(regs))
+
+#define cpuid_leaf(leaf, regs)				\
+	BUILD_BUG_ON(sizeof(*(regs)) != 16);		\
+	__cpuid_read(leaf, 0, (u32 *)(regs))
+
+static inline void __cpuid_read_reg(unsigned int leaf, unsigned int subleaf,
+				    enum cpuid_regs_idx regidx, u32 *reg)
+{
+	u32 regs[4];
+
+	__cpuid_read(leaf, subleaf, regs);
+	*reg = regs[regidx];
+}
+
+#define cpuid_subleaf_reg(leaf, subleaf, regidx, reg)		\
+	BUILD_BUG_ON(sizeof(*(reg)) != 4);			\
+	__cpuid_read_reg(leaf, subleaf, regidx, (u32 *)(reg))
+
+#define cpuid_leaf_reg(leaf, regidx, reg)			\
+	BUILD_BUG_ON(sizeof(*(reg)) != 4);			\
+	__cpuid_read_reg(leaf, 0, regidx, (u32 *)(reg))
+
 static __always_inline bool cpuid_function_is_indexed(u32 function)
 {
 	switch (function) {