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bluepill/VMCS-GUEST.md

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Intel Processor Info

Processors: (two xeon cpus)
    Processor	Intel(R) Xeon(R) CPU           X5650  @ 2.67GHz, 2668 Mhz, 6 Core(s), 12 Logical Processor(s)
    Processor	Intel(R) Xeon(R) CPU           X5650  @ 2.67GHz, 2668 Mhz, 6 Core(s), 12 Logical Processor(s)

VMCS - Guest Fields

26.3.1.1 Checks on Guest Control Registers, Debug Registers, and MSRs

Checks on Guest Control Registers

  • The CR0 field must not set any bit to a value not supported in VMX operation (see Section 23.8). The following are exceptions: ✅

    • Bit 0 (corresponding to CR0.PE) and bit 31 (PG) are not checked if the “unrestricted guest” VM-execution control is 1.

    • Bit 29 (corresponding to CR0.NW) and bit 30 (CD) are never checked because the values of these bits are not changed by VM entry; see Section 26.3.2.1.

  • The following checks are performed on processors that support Intel 64 architecture:

    • If the “IA-32e mode guest” VM-entry control is 1, bit 31 in the CR0 field (corresponding to CR0.PG) and bit 5 in the CR4 field (corresponding to CR4.PAE) must each be 1. ✅

    • If the “IA-32e mode guest” VM-entry control is 0, bit 17 in the CR4 field (corresponding to CR4.PCIDE) must be 0. (this value is one in my entry controls) ✅

    • The CR3 field must be such that bits 63:52 and bits in the range 51:32 beyond the processor’s physicaladdress width are 0. ✅

  • The CR4 field must not set any bit to a value not supported in VMX operation (see Section 23.8). ✅

guest cr0: 0x0000000080050033 0b1000 0000 0000 0101 0000 0000 0011 0011
guest cr3: 0x00000000001AD000
guest cr4: 0x00000000000026F8 0b0010 0110 1111 1000
Checks on Guest MSRs

  • If the “load debug controls” VM-entry control is 1, bits reserved in the IA32_DEBUGCTL MSR must be 0 in the field for that register. (this is not set in vm entry control fields in my vmcs...) ✅

  • The IA32_SYSENTER_ESP field and the IA32_SYSENTER_EIP field must each contain a canonical address. (this is MSR is zero) ✅

"In 64-bit mode, an address is considered to be in canonical form if address bits 63 through to the most-significant implemented bit by the microarchitecture are set to either all ones or all zeros..."

VMCS_GUEST_DEBUGCTL: 0x0000000000000000
VMCS_GUEST_SYSENTER_CS: 0x0000000000000000
VMCS_GUEST_SYSENTER_EIP: 0x0000000000000000
VMCS_GUEST_SYSENTER_ESP: 0x0000000000000000

26.3.1.2 Checks on Guest Segment Registers

This section specifies the checks on the fields for CS, SS, DS, ES, FS, GS, TR, and LDTR.

  • Selector fields.

    • TR. The TI flag (bit 2) must be 0. ✅
    • LDTR. If LDTR is usable, the TI flag (bit 2) must be 0. ✅
    • SS. If the guest will not be virtual-8086 and the “unrestricted guest” VM-execution control is 0, the RPL ✅ (bits 1:0) must equal the RPL of the selector field for CS. ✅

  • Base-address fields.

    • TR, FS, GS. The address must be canonical. ✅
    • CS. Bits 63:32 of the address must be zero. ✅
    • SS, DS, ES. If the register is usable, bits 63:32 of the address must be zero. ✅

  • Access-rights fields for CS, SS, DS, ES, FS, GS.

    • CS Bits 3:0 (Type): must be 9, 11, 13, or 15 (accessed code segment). ✅
    • SS. If SS is usable, the Type must be 3 or 7 (read/write, accessed data segment). ✅
    • DS, ES, FS, GS. The following checks apply if the register is usable ✅
      • Bit 0 of the Type must be 1 (accessed). ✅
      • If bit 3 of the Type is 1 (code segment), then bit 1 of the Type must be 1 (readable). ✅
    • Bit 4 (S). If the register is CS or if the register is usable, S must be 1 ✅
es selector: 0x000000000000002B
 	 - es.index: 5
	 - es.request_privilege_level: 3
	 - es.table: 0
es base address: 0x0000000000000000
es limit: 0x00000000FFFFFFFF
es rights: 0x000000000000C0F3
		- es_rights.available_bit: 0
		- es_rights.default_big: 1
		- es_rights.descriptor_privilege_level: 3
		- es_rights.descriptor_type: 1
		- es_rights.granularity: 1
		- es_rights.long_mode: 0
		- es_rights.present: 1
		- es_rights.type: 3
		- es_rights.unusable: 0
		
		
fs selector: 0x0000000000000053
		- fs.index: 10
		- fs.request_privilege_level: 3
		- fs.table: 0
fs base address: 0x0000000000000000
fs base (from readmsr): 0x0000000000000000
fs limit: 0x0000000000003C00
fs rights: 0x00000000000040F3
		- fs_rights.available_bit: 0
		- fs_rights.default_big: 1
		- fs_rights.descriptor_privilege_level: 3
		- fs_rights.descriptor_type: 1
		- fs_rights.granularity: 0
		- fs_rights.long_mode: 0
		- fs_rights.present: 1
		- fs_rights.type: 3
		- fs_rights.unusable: 0
		
		
gs selector: 0x000000000000002B
		- gs.index: 5
		- gs.request_privilege_level: 3
		- gs.table: 0
gs base address: 0x0000000000000000
gs base (from readmsr): 0xFFFFF80365406000
gs limit: 0x00000000FFFFFFFF
gs rights: 0x000000000000C0F3
		- gs_rights.available_bit: 0
		- gs_rights.default_big: 1
		- gs_rights.descriptor_privilege_level: 3
		- gs_rights.descriptor_type: 1
		- gs_rights.granularity: 1
		- gs_rights.long_mode: 0
		- gs_rights.present: 1
		- gs_rights.type: 3
		- gs_rights.unusable: 0
		
		
ss selector: 0x0000000000000018
		- ss.index: 3
		- ss.request_privilege_level: 0
		- ss.table: 0
ss base address: 0x0000000000000000
ss limit: 0x0000000000000000
ss rights: 0x0000000000004093
		- ss_rights.available_bit: 0
		- ss_rights.default_big: 1
		- ss_rights.descriptor_privilege_level: 0
		- ss_rights.descriptor_type: 1
		- ss_rights.granularity: 0
		- ss_rights.long_mode: 0
		- ss_rights.present: 1
		- ss_rights.type: 3
		- ss_rights.unusable: 0
		
		
cs selector: 0x0000000000000010
		- cs.index: 2
		- cs.request_privilege_level: 0
		- cs.table: 0
cs base address: 0x0000000000000000
cs limit: 0x0000000000000000
cs rights: 0x000000000000209B
		- cs_rights.available_bit: 0
		- cs_rights.default_big: 0
		- cs_rights.descriptor_privilege_level: 0
		- cs_rights.descriptor_type: 1
		- cs_rights.granularity: 0
		- cs_rights.long_mode: 1
		- cs_rights.present: 1
		- cs_rights.type: 11
		- cs_rights.unusable: 0
		
		
ds selector: 0x000000000000002B
		- ds.index: 5
		- ds.request_privilege_level: 3
		- ds.table: 0
ds base address: 0x0000000000000000
ds limit: 0x00000000FFFFFFFF
ds rights: 0x000000000000C0F3
		- ds_rights.available_bit: 0
		- ds_rights.default_big: 1
		- ds_rights.descriptor_privilege_level: 3
		- ds_rights.descriptor_type: 1
		- ds_rights.granularity: 1
		- ds_rights.long_mode: 0
		- ds_rights.present: 1
		- ds_rights.type: 3
		- ds_rights.unusable: 0

  • TR Access Rights Checks. The different sub-fields are considered separately:

    • Bits 3:0 (Type).

      • If the guest will not be IA-32e mode, the Type must be 3 (16-bit busy TSS) or 11 (32-bit busy TSS). ✅
      • If the guest will be IA-32e mode, the Type must be 11 (64-bit busy TSS). ✅

    • Bit 4 (S). S must be 0. ✅

    • Bit 7 (P). P must be 1. ✅

    • Bits 11:8 (reserved). These bits must all be 0. ✅

    • Bit 15 (G).

      • If any bit in the limit field in the range 11:0 is 0, G must be 0. ✅
      • If any bit in the limit field in the range 31:20 is 1, G must be 1. ✅

    • Bit 16 (Unusable). The unusable bit must be 0. ✅

    • Bits 31:17 (reserved). These bits must all be 0. ✅

tr selector: 0x0000000000000040
		- tr.index: 8
		- tr.request_privilege_level: 0
		- tr.table: 0
tr base address: 0xFFFFF8036EA5F000
tr limit: 0x0000000000000067
tr rights: 0x000000000000008B
		- tr_rights.available_bit: 0
		- tr_rights.default_big: 0
		- tr_rights.descriptor_privilege_level: 0
		- tr_rights.descriptor_type: 0
		- tr_rights.granularity: 0
		- tr_rights.long_mode: 0
		- tr_rights.present: 1
		- tr_rights.type: 11
		- tr_rights.unusable: 0

  • LDTR Access Rights Checks. The following checks on the different sub-fields apply only if LDTR is usable:

    • Bits 3:0 (Type). The Type must be 2 (LDT). ✅
    • Bit 4 (S). S must be 0. ✅
    • Bit 7 (P). P must be 1. ✅
    • Bits 11:8 (reserved). These bits must all be 0. ✅
    • Bit 15 (G).
      • If any bit in the limit field in the range 11:0 is 0, G must be 0. ✅
      • If any bit in the limit field in the range 31:20 is 1, G must be 1. ✅
    • Bits 31:17 (reserved). These bits must all be 0. ✅
ldt selector: 0x0000000000000000
		- ldt.index: 0
		- ldt.request_privilege_level: 0
		- ldt.table: 0
ldt base address: 0xFFFFF8036EA5F000
ldt limit: 0x0000000000000067
ldt rights: 0x000000000000008B
		- ldt_rights.available_bit: 0
		- ldt_rights.default_big: 0
		- ldt_rights.descriptor_privilege_level: 0
		- ldt_rights.descriptor_type: 0
		- ldt_rights.granularity: 0
		- ldt_rights.long_mode: 0
		- ldt_rights.present: 1
		- ldt_rights.type: 11
		- ldt_rights.unusable: 0