HV:INSTR:Rearrange register names in the enum cpu_reg_name

In the current "enum cpu_reg_name", there are 16-bit segment
register names, 16-bit descriptor table register names, and
16-bit task register names. These 16-bit register names are
defined among the 64 bit register names. To access these
16-bit fields in VMCS and 32 bit fields in VMCS, more
condition statements need to be used.

Update 16-bit register names position to simplify conditions
in vm_get_register and vm_set_register since different
fields size accessing in VMCS by different vmread/vmwrite
opreation.

Note: After checking the current implementation, the register names of
the same kind of registers (general registers, control registers,
segment registers etc) need to be defined in order, some code checks
the range by using this order. But different kinds of register
names as group, this group position can be adjusted to simplify
conditions.
The follwoing register names group need to be considered in current
implemetation:
(1) General register names group: CPU_REG_RAX~CPU_REG_RDI;
(2) Non-General register names group:CPU_REG_CR0~CPU_REG_LAST;
(3) segment register names group:CPU_REG_ES~CPU_REG_GS.

V1-->V2:
	This is new part of this patch serial created in
	V2 to rearrange register names as needed.
V2--V3:
	Update comment information.
V3-->V4:
	Define CPU_REG_NATURAL_LAST and CPU_REG_64BIT_LAST to
	make condition more understandable.

Signed-off-by: Xiangyang Wu <xiangyang.wu@intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>

hypervisor/arch/x86/guest/instr_emul_wrapper.h

@@ -31,8 +31,27 @@
 #define INSTR_EMUL_WRAPPER_H
 #include <cpu.h>
 
-/*
+/**
+ *
  * Identifiers for architecturally defined registers.
+ *
+ * These register names is used in condition statement.
+ * Within the following groups,register name need to be 
+ * kept in order:
+ * General register names group (CPU_REG_RAX~CPU_REG_RDI);
+ * Non general register names group (CPU_REG_CR0~CPU_REG_LAST);
+ * Segement register names group (CPU_REG_ES~CPU_REG_GS).
+ *
+ * CPU_REG_NATURAL_LAST indicates in the non general register names
+ * group the register name (less than CPU_REG_NATURAL_last) is 
+ * corresponds to the natural width field in VMCS;
+ *
+ * CPU_REG_64BIT_LAST indicates in the non general register names
+ * group the register name (less than CPU_REG_64BIT_LAST and more than
+ * CPU_REG_NATURAL_last) corresponds to the 64-bit field in VMCS.
+ *
+ * CPU_REG_LAST indicates the last register name.
+ *
  */
 enum cpu_reg_name {
 	CPU_REG_RAX,
@@ -51,12 +70,20 @@ enum cpu_reg_name {
 	CPU_REG_R15,
 	CPU_REG_RDI,
 	CPU_REG_CR0,
+	CPU_REG_CR2,
 	CPU_REG_CR3,
 	CPU_REG_CR4,
 	CPU_REG_DR7,
 	CPU_REG_RSP,
 	CPU_REG_RIP,
 	CPU_REG_RFLAGS,
+	CPU_REG_NATURAL_LAST,
+	CPU_REG_EFER,
+	CPU_REG_PDPTE0,
+	CPU_REG_PDPTE1,
+	CPU_REG_PDPTE2,
+	CPU_REG_PDPTE3,
+	CPU_REG_64BIT_LAST,
 	CPU_REG_ES,
 	CPU_REG_CS,
 	CPU_REG_SS,
@@ -67,12 +94,6 @@ enum cpu_reg_name {
 	CPU_REG_TR,
 	CPU_REG_IDTR,
 	CPU_REG_GDTR,
-	CPU_REG_EFER,
-	CPU_REG_CR2,
-	CPU_REG_PDPTE0,
-	CPU_REG_PDPTE1,
-	CPU_REG_PDPTE2,
-	CPU_REG_PDPTE3,
 	CPU_REG_LAST
 };