[Qemu-devel] Direct guest device access from nested guest

["Lluís Vilanova" <vilanova@ac.upc.edu>]

Hi,

I want to get the following setup, but don't know how (or if it's even
possible):

* A guest VM with two AHCI controllers, with one device each. One of the AHCI
  controllers provides the VM's disk ("system"), while the other provides
  another disk ("nested") and uses a different emulation driver in QEMU (ahci2):

  host$ qemu-system-x86_64 -enable-kvm \
            -drive id=system,file=system.img,if=none \
            -device ahci,id=ahci \
            -device ide-drive,drive=system,bus=ahci.0 \
            -drive id=nested,file=nested.img,if=none \
            -device ahci2,id=ahci2 \
            -device ide-drive,drive=nested,bus=ahci2.0

* A nested guest VM using the guest's (its host) AHCI2 controller.

  I've tried assigning the AHCI2 device to the nested guest using "pci-assign"
  and "vfio", but without any luck.

  The culprit of the problem seems to be I cannot get the nested guest to have
  an IOMMU.

Is it possible to give a nested guest direct access to a device on the guest?
(more specifically, an AHCI controller).


Thanks a lot,
  Lluis

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