On 1 April 2017 at 01:46, Eduardo Habkost <ehabk...@redhat.com> wrote: > commit 33cd52b5d7b9adfd009e95f07e6c64dd88ae2a31 unset > cannot_instantiate_with_device_add_yet in TYPE_SYSBUS, making > all kinds of untested devices available to -device and > device_add. > > The problem with that is: setting has_dynamic_sysbus on a > machine-type lets it accept all the 288 sysbus device types we > have in QEMU, and most of them were never meant to be used with > -device. That's a lot of untested code. > > Fortunately today we have just a few has_dynamic_sysbus=1 > machines: virt, pc-q35-*, ppce500, and spapr. > > virt, ppce500, and spapr have extra checks to ensure just a few > device types can be instantiated: > > * virt supports only TYPE_VFIO_CALXEDA_XGMAC, TYPE_VFIO_AMD_XGBE. > * ppce500 supports only TYPE_ETSEC_COMMON. > * spapr supports only TYPE_SPAPR_PCI_HOST_BRIDGE. > > q35 has no code to block unsupported sysbus devices, however, and > accepts all device types. Fortunately, only the following 20 > device types are compiled into the qemu-system-x86_64 and > qemu-system-i386 binaries: > > * allwinner-ahci > * amd-iommu > * cfi.pflash01 > * esp > * fw_cfg_io > * fw_cfg_mem > * generic-sdhci > * hpet > * intel-iommu > * ioapic > * isabus-bridge > * kvmclock > * kvm-ioapic > * kvmvapic > * SUNW,fdtwo > * sysbus-ahci > * sysbus-fdc > * sysbus-ohci > * unimplemented-device > * virtio-mmio > > Instead of requiring each machine-type with has_dynamic_sysbus=1 > to implement its own mechanism to block unsupported devices, we > can use the user_creatable flag to ensure we won't let the user > plug anything that will never work.
How does this work? Which devices can be dynamically plugged is machine dependent. You can't dynamically-plug an intel-iommu on the ARM virt board, and you can't dynamically-plug the vfio-calxeda-xgmac on the spapr board, and so on. So I don't see how we can just have a flag on the device itself that controls whether it can be dynamically plugged. So I'm definitely coming around to the opinion that it's just a bug in the q35 board that it doesn't have any device whitelisting, and we should fix that. thanks -- PMM
