On 10/07/2017 17:48, Nadav Amit wrote: >>> >>> Any proposal is a great appreciated. :) > I don’t see a (very) easy solution. The code was (apparently) never built to > deal with a task switch during an instruction emulation. > > AFAIU kvm_task_switch() expects information about the task-switch from the > CPU “task-switch assist” mechanisms, and this information (or even the fact > that a task-switch is needed due to an exception) are unavailable from the > instruction emulator. The instruction emulator itself does not know to > emulate task-switches, e.g., during far CALL and JMP. > > A complete solution is therefore complicated and requires some work. Your > specific problem may be addressed by detecting the injection of an exception > while having invalid guest state in vm86 in vmx_queue_exception() or in > handle_invalid_guest_state(), and emulating the “task-switch assist” > mechanism.
I agree, the right solution would be to read the IDT in vmx_queue_exception if vmx->emulation_required, and inject the exception manually. It would be an extension of what kvm_inject_realmode_interrupt already does. Paolo
