PIO/MMIO access from guest

Hi all,

I would like to access the configuration registers of my passthrough device from an unmodified guest under KVM via MMIO/PIO directly. Is there any option to configure the guest in this way? I know that you can do this with the ioports=[''] option in case of Xen, but I could not find any such option until now for KVM. I also read that

[+] PIO can be passed directly via VMCS I/O bitmaps [+] MMIO can be passed directly via mapping device BARs to guest [+] Some PIO/MMIO accesses must be trapped (PCI config space)

Can I do this with some configurations without recompiling the kernel?

Thank you!
-gabor