x86: Add function to modify CR3 register

Register CR3 holds the physical address of paging-structure hierarchy.
Add functions to enable read/write of this register.

Change-Id: Icfd8f8e32833d2c80cefc8f930d6eedbfeb5e3ee
Signed-off-by: Naresh G Solanki <naresh.solanki@intel.com>
Reviewed-on: https://review.coreboot.org/25478
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/cpu/x86/cr.h

@@ -59,6 +59,27 @@ static alwaysinline void write_cr0(CRx_TYPE data)
 	);
 }
 
+static alwaysinline CRx_TYPE read_cr3(void)
+{
+	CRx_TYPE value;
+	__asm__ __volatile__ (
+		"mov %%cr3, %0"
+		: CRx_RET(value)
+		:
+		: COMPILER_BARRIER
+	);
+	return value;
+}
+
+static alwaysinline void write_cr3(CRx_TYPE data)
+{
+	__asm__ __volatile__ (
+		"mov %0, %%cr3"
+		:
+		: CRx_IN(data)
+		: COMPILER_BARRIER
+	);
+}
 static alwaysinline CRx_TYPE read_cr4(void)
 {
 	CRx_TYPE value;