Create the iommu device with '-device intel-iommu' instead of '-machine,iommu=on'.
The device is part of the machine properties because we wanted to ensure it is created before any other PCI device. The alternative is to skip the bus_master_enable_region at the time the device is created. We can create this region at machine_done phase. (patch 1) Patch 2 moves the init proces into iommu's realize function. Then we need to enable sysbus devices for PC machines (patch 3). This creates a new problem since we have now a bunch of new devices that can be created with -device on Q35: name "q35-pcihost", bus System name "sysbus-ohci", bus System, desc "OHCI USB Controller" name "allwinner-ahci", bus System name "cfi.pflash01", bus System name "esp", bus System name "SUNW,fdtwo", bus System name "sysbus-ahci", bus System name "sysbus-fdc", bus System name "vfio-amd-xgbe", bus System, desc "VFIO AMD XGBE" name "vfio-calxeda-xgmac", bus System, desc "VFIO Calxeda XGMAC" name "virtio-mmio", bus System name "fw_cfg", bus System name "fw_cfg_io", bus System name "fw_cfg_mem", bus System name "generic-sdhci", bus System name "hpet", bus System name "i440FX-pcihost", bus System name "intel-iommu", bus System name "ioapic", bus System name "isabus-bridge", bus System name "kvm-ioapic", bus System name "kvmclock", bus System name "kvmvapic", bus System name "pxb-host", bus System Took care of the ones creating immediate issues (like crashes) by marking them as 'cannot_instantiate_with_device_add_yet'. I didn't mark them all because: - libvirt will mask them anyway - some of them have already a "protection" in place - it is possible that some of them can be actually used with -device on other platform. - those are not 'interesting' scenarios. If somebody spots devices in the list that cannot be added with -device on any platform please let me know and I'll mark them. v1 -> v2: - Enable bus_master also on init if the guest OS already booted to enable hotplug (Paolo). - Add a machine_done notifier to PCIBus instead of adding functionality for q35 machine_done callback. The main reason is we don't want to replicate the code for all platforms that support PCI and is also cleaner this way. - Added 'cannot_instantiate_with_device_add_yet' to sysbus devices that lead to crashes if added with -device. - Rebased on master Thanks, Marcel Marcel Apfelbaum (2): hw/pci: delay bus_master_enable_region initialization hw/iommu: enable iommu with -device q35: allow dynamic sysbus hw/core/machine.c | 20 ---------------- hw/i386/intel_iommu.c | 17 ++++++++++++++ hw/i386/pc_q35.c | 1 + hw/pci-bridge/pci_expander_bridge.c | 1 + hw/pci-host/piix.c | 1 + hw/pci-host/q35.c | 29 +---------------------- hw/pci/pci.c | 46 +++++++++++++++++++++++++++++-------- include/hw/pci/pci_bus.h | 2 ++ qemu-options.hx | 3 --- 9 files changed, 59 insertions(+), 61 deletions(-) -- 2.4.3