Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
Vol. 3 23-23
VM EXITS
For VM exits due to attempts to execute VMREAD or VMWRITE, the field has
the format is given in Table 23-12.
26:23 BaseReg (encoded as IndexReg above)
Undefined for instructions with no base register (bit 27 is set).
27 BaseReg invalid (0 = valid; 1 = invalid)
31:28 Undefined.
Table 23-12. Format of the VM-Exit Instruction-Information Field as Used for
VMREAD and VMWRITE
Bit Position(s) Content
1:0 Scaling:
0: no scaling
1: scale by 2
2: scale by 4
3: scale by 8 (used only on processors that support Intel 64 architecture)
Undefined for register instructions (bit 10 is set) and for memory instructions with
no index register (bit 10 is clear and bit 22 is set).
2Undefined.
6:3 Reg1:
0= RAX
1= RCX
2= RDX
3= RBX
4= RSP
5= RBP
6= RSI
7= RDI
8–15 represent R8–R15, respectively (used only on processors that support
Intel 64 architecture)
Undefined for memory instructions (bit 10 is clear).
9:7 Address size:
0: 16-bit
1: 32-bit
2: 64-bit (used only on processors that support Intel 64 architecture)
Other values not used. Undefined for register instructions (bit 10 is set).
Table 23-11. Format of the VM-Exit Instruction-Information Field as Used for
VMCLEAR, VMPTRLD, VMPTRST, and VMXON (Contd.)
Bit Position(s) Content