<div align="center">
  <img width="1000" height="auto" src="https://imgur.com/b1bYNZU.png"/>
  <p>Figure 1. First ever vmexit...</p>
</div>

# Bluepill

Bluepill is an Intel type-2 research hypervisor. This project is purely for educational purposes and is designed to run on Windows 10 systems.
This project uses WDK and thus Windows Kernel functions to facilitate vmxlaunch.

### VMCS

This section of the readme just contains notes and a list of things I stumbled on and took me a while to figure out and fix.

##### VMCS Controls

* One of the mistakes I made early on was setting bits high after applying high/low MSR values. For example my xeons dont support Intel Processor Trace (Intel PT) and I was setting `entry_ctls.conceal_vmx_from_pt = true` after applying the MSR high/low masks. This caused vmxerror #7 (invalid vmcs controls). Now i set the bit high before i apply the high/low bit mask so if my hypervisor runs on a cpu that has Intel PT support it will be concealed from Intel PT.
* My xeons also dont support xsave/xrstor and I was setting enable_xsave in secondary processor based vmexit controls after applying `IA32_VMX_PROCBASED_CTLS2` high/low bitmask. Which caused vmxerror #7 (invalid vmcs controls).

Dump of VMCS control fields can be found [here](https://githacks.org/_xeroxz/bluepill/-/blob/master/VMCS-CONTROLS.md). This is not required, but for learning its nice to
see exactly what the MSR masks are, and what VMCS field's are enabled after you apply high/low bit masks.

##### VMCS Guest State

* After getting my first vmexit the exit reason was 0x80000021 (invalid guest state). I thought it was segmentation code since I've never done anything with segments before but after a few days of checking every single segment check in chapter 26 section 3, I continued reading the guest requirements in chapter 24  section 4, part 2 goes over non-register states and I was not setting any of these `VMCS_GUEST_ACTIVITY_STATE`, `VMCS_GUEST_INTERRUPTIBILITY_STATE`, or `VMCS_GUEST_PENDING_DEBUG_EXCEPTIONS`. 

Dump of VMCS guest fields can be found [here](https://githacks.org/_xeroxz/bluepill/-/blob/master/VMCS-GUEST.md).