How to troubleshoot VT stuck?

[Yalneh]

Hi, when I write my own VT driver, the system often freezes. This happens when the program runs for a while and then suddenly freezes. How do you troubleshoot these freeze issues when developing dbvm?

[cheat-engine]

serial port connection with a different system

it has some debug functions like showing rhe state, last couple of events and memory reading/ disassembling

[Yalneh]

serial port connection with a different system

it has some debug functions like showing rhe state, last couple of events and memory reading/ disassembling

Thank you very much for taking the time to reply. Does dbvm have a watchdog-like mechanism to prevent the system from freezing?

[cheat-engine]

not specifically. But while debugging I do have it check the serial port for the 'b' key on each vmexit and if it's received halt and go into the debugging interface as mentioned earlier.

Though normally when it freezes it just means it entered an invalid state and doesn't know how to continue. In which case DBVM will quit and dump all the data

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You probably already know this, but just putting this here anyhow:
One common mistake people make when running their VM inside of the same running windows instance instead of outside of it in their own contained OS is that you have to be careful not to use any windows provided API's

Imagine what would happen when windows goes into it's patchguard routine. It enters a high interrupt level and obtains spinlocks and does some anti debugging stuff like int1 and other stuff which will likely trigger vmexits. So your code gets called.
Now let's assume you did the basics correct and have all your driver code in non-paged memory (if you didn't you're going to crash as soon as a paged out page gets accessed)
Your code is also running at interrupt disabled high dpc level, but it's impossible for you to lower that down as windows still have some mutexes/spinlocks locked, so pretty much only a handful of functions are available. Don't even try to allocate memory (you'll have to write your own memory manager)

[Yalneh]

serial port connection with a different system

it has some debug functions like showing rhe state, last couple of events and memory reading/ disassembling

Modern PC desktops and laptops no longer have COM1 ports, right?

[cheat-engine]

depends. There are still heavy duty grade mainboards that have a com1 port header you can connect a port on

otherwise there's always pci/pcie serial ports like startech, but you'll have to pick the correct io ports, it's not the default port numbers then. You can see the port range in the resources tab in taskmanager.