SMM dual-monitor treatment

SMM dual-monitor treatment

How to return to executive monitor from SMM monitor after activating dual-monitor treatment?
VMLAUNCH on SMM-transfer VMCS reports "VMLAUNCH with non-clear VMCS", VMRESUME on SMM-transfer VMCS reports "VMRESUME with non-launched VMCS".

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Here's what I was told:

"At first VmEntry, we need use VmLaunch. For the next VmEntry, just use VmResume."

Is that enough to clarify?

David Ott

Quoting David Ott (Intel)
Here's what I was told:

"At first VmEntry, we need use VmLaunch. For the next VmEntry, just use VmResume."

Is that enough to clarify?

David Ott

That's what I wrote in my post. But at first VmEntry VmLaunch reports "VMLAUNCH with non-clear VMCS".
Or should I not use "SMM-transfer VMCS" for returning to executive monitor? How then should I use this "SMM-transfer VMCS"?

I can't really help you with SMM mode, but did you call vmclear before your vmlaunch instruction and your vmwrites to your vmcs?

Another comment I received that may be useful isbelow:

"The SMM monitor could use VMPTRST to determine the location of the VMCS that was set up prior to VMCALL) and then VMCLEAR it. It could then copy 4KB of data from the address identified by VMPTRST to a region in SMRAM and then execute first VMCLEAR and then VMPTRLD on that SMRAM region. It should then VMWRITE the following: (1) VM-entry controls to manage a return from SMM properly; (2) VM-exit controls to manage future invocations of the SMM monitor; and (3) host state to manage future invocations of the SMM monitor. It could VMWRITE the saved guest EIP to increment past the VMCALL instruction (the length of which was reported in the VM-exit instruction-length field). Upon conclusion of its initialization, the SMM monitor could use VMLAUNCH on the new VMCS to return to the invoking code."

There was also a question as to whether the SMM monitoristrying to return tothe same VMCS that was used to invoke it

David Ott

My SMM monitor works, but i have a new problem:
When SMM VM-exit occures from VMX-root mode (by receiving SMI) immediately after execution command "MOV SS,AX", then does not happen any VM-exits after VMRESUME in SMM monitor. What could it be?

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