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

Table Of Contents
Vol. 3 25-25
SYSTEM MANAGEMENT
SS.RPL SS.DPL;
FI;
restore current VMCS pointer;
FI;
leave SMM;
IF logical processor will be in VMX operation or in SMX operation after RSM
THEN block A20M and leave A20M mode;
FI;
FI;
RSM unblocks SMIs. It restores the state of blocking by NMI (see Table 20-3 in
Section 20.4.2) as follows:
If the RSM is not to VMX non-root operation or if the “virtual NMIs” VM-execution
control will be 0, the state of NMI blocking is restored normally.
If the RSM is to VMX non-root operation and the “virtual NMIs” VM-execution
control will be 1, NMIs are not blocked after RSM. The state of virtual-NMI
blocking is restored as part of VMX-critical state.
INIT signals are blocked after RSM if and only if the logical processor will be in VMX
root operation.
If RSM returns a logical processor to VMX non-root operation, it re-establishes the
controls associated with the current VMCS. If the “interrupt-window exiting”
VM-execution control is 1, a VM exit occurs immediately after RSM if the enabling
conditions apply. The same is true for the “NMI-window exiting” VM-execution
control. Such VM exits occur with their normal priority. See Section 21.3.
If an MTF VM exit was pending at the time of the previous SMI, an MTF VM exit is
pending on the instruction boundary following execution of RSM. The following items
detail the treatment of MTF VM exits that may be pending following RSM:
System-management interrupts (SMIs), INIT signals, and higher priority events
take priority over these MTF VM exits. These MTF VM exits take priority over
debug-trap exceptions and lower priority events.
These MTF VM exits wake the logical processor if RSM caused the logical
processor to enter the HLT state (see Section 25.10). They do not occur if the
logical processor just entered the shutdown state.
25.14.3 Protection of CR4.VMXE in SMM
Under the default treatment, CR4.VMXE is treated as a reserved bit while a logical
processor is in SMM. Any attempt by software running in SMM to set this bit causes a
general-protection exception. In addition, software cannot use VMX instructions or
enter VMX operation while in SMM.