Hello,
I've had this issue on my ESXi host since version 6. I have an AMD Radeon 6450 GPU set as a passthrough device to a specific VM. Everything works great except for when that particular VM is powered off. The ESXi host freezes/stops responding and must be hard power cycled to get it operational again. I did some research and it appears that it's a problem with the hypervisor sending a reset to the PCI-E bus not executing properly during power off. This isn't an issue when the VM is just rebooting (not full power off).
I was hoping upgrading to ESXi 6.5 would resolve this issue but alas, it hasn't.
Here are more specifics regarding my host:
* Supermicro X9SRL-F Server Motherboard
* Intel Xeon E5-2690 CPU
* 32GB DDR3 RAM (not ECC)
* 8TB of local storage connected via an LSI MegaRAID 9240-8i controller
* AMD Radeon 6450 GPU
Any guidance on this issue would be greatly appreciated. I've seen some suggestions on dropping down to ESXi 5.5 but I would prefer not doing that!
Thanks,
Chris