Bhyve

[Peter Grehan]

Hi Kumar,

> I have just started developing something in FreeBSD. I have done few
> changes in the memory part. Before that i just want to confirm that for the
> guest machines for the system memory there is only one object used. If the
> memory is greater than he lowmem remaining is allocated in highmem. The
> memory between these two is used for MMIO which is a separate object.

  It isn't really an object but a hole in the address space. Any access 
to that region results in an EPT-violation exit from the VM, and a trip 
through the bhyve instruction emulation path.

> When I did few changes FreeBSD vm booted fine. But when i tried windows it was
> vm_run error and value is EFAULT. The EFAULT is because of the GPA that
> belongs to the MMIO region and the exact value is 4276093104 and fails in
> the function vm_handle_inst_emul.   I would like to know why is this
> different in both the cases.

  4276093104 is 0xfee000b0, which is local APIC EOI register. There 
haven't been any issues with accessing this from Windows in the past - 
is this an earlier version than Vista ? (e.g. server 2k3)

later,

Peter.