Bionic

$ gdb /usr/bin/qemu-system-x86_64
(gdb) handle SIGUSR1 noprint nostop
(gdb) b machine_register_compat_props
(gdb) run -m 128 -M pc-i440fx-wily,accel=kvm --nodefaults --nographic --monitor stdio -device virtio-balloon-pci,id=balloon0
(gdb) fin

(gdb) set $c=(GList *)global_props
(gdb) define report
>p *((GlobalProperty*)$c->data)
>set $c=$c->next
>end
(gdb) report

On qemu 2.11 delivered

"virtio-mouse-device" "wheel-axis" "false", user_provided = false, used = false
"virtio-tablet-device" "wheel-axis" "false", user_provided = false, used = false
"e1000" "romfile" "compat-256k-efi-e1000.rom", user_provided = false, used = false
"ne2000" "romfile" "compat-256k-efi-ne2k_pci.rom", user_provided = false, used = false
"pcnet" "romfile" "compat-256k-efi-pcnet.rom", user_provided = false, used = false
"rtl8139" "romfile" "compat-256k-efi-rtl8139.rom", user_provided = false, used = false
"virtio-net-pci" "romfile" "compat-256k-efi-virtio.rom", user_provided = false, used = false
"x86_64-cpu" "x-hv-max-vps" "0x40", user_provided = false, used = true
"i440FX-pcihost" "x-pci-hole64-fix" "off", user_provided = false, used = true
"q35-pcihost" "x-pci-hole64-fix" "off", user_provided = false, used = false
"pci-bridge" "shpc" "off", user_provided = false, used = false
"intel-iommu" "pt" "off", user_provided = false, used = false
"virtio-net-device" "x-mtu-bypass-backend" "off", user_provided = false, used = false
"pcie-root-port" "x-migrate-msix" "false", user_provided = false, used = false
"mch" "extended-tseg-mbytes" "0", user_provided = false, used = false
"fw_cfg_mem" "x-file-slots" "0x10", user_provided = false, used = false
"fw_cfg_io" "x-file-slots" "0x10", user_provided = false, used = true
"pflash_cfi01" "old-multiple-chip-handling" "on", user_provided = false, used = false
"pci-bridge" "shpc" "on", user_provided = false, used = false
"pci-device" "x-pcie-extcap-init" "off", user_provided = false, used = true
"virtio-pci" "x-pcie-deverr-init" "off", user_provided = false, used = true
"virtio-pci" "x-pcie-lnkctl-init" "off", user_provided = false, used = true
"virtio-pci" "x-pcie-pm-init" "off", user_provided = false, used = true
"cirrus-vga" "vgamem_mb" "8", user_provided = false, used = false
"isa-cirrus-vga" "vgamem_mb" "8", user_provided = false, used = false
"x86_64-cpu" "tcg-cpuid" "off", user_provided = false, used = true
"kvmclock" "x-mach-use-reliable-get-clock" "off", user_provided = false, used = true
"ICH9-LPC" "x-smi-broadcast" "off", user_provided = false, used = false
"x86_64-cpu" "vmware-cpuid-freq" "off", user_provided = false, used = true
"Haswell-x86_64-cpu" "stepping" "1", user_provided = false, used = false
"virtio-pci" "page-per-vq" "on", user_provided = false, used = true
"virtio-serial-device" "emergency-write" "off", user_provided = false, used = false
"ioapic" "version" "0x11", user_provided = false, used = false
"intel-iommu" "x-buggy-eim" "true", user_provided = false, used = false
"virtio-pci" "x-ignore-backend-features" "on", user_provided = false, used = true
"x86_64-cpu" "l3-cache" "off", user_provided = false, used = true
"x86_64-cpu" "full-cpuid-auto-level" "off", user_provided = false, used = true
"Opteron_G3-x86_64-cpu" "family" "15", user_provided = false, used = false
"Opteron_G3-x86_64-cpu" "model" "6", user_provided = false, used = false
"Opteron_G3-x86_64-cpu" "stepping" "1", user_provided = false, used = false
"isa-pcspk" "migrate" "off", user_provided = false, used = true
"virtio-mmio" "format_transport_address" "off", user_provided = false, used = false
"virtio-pci" "disable-modern" "on", user_provided = false, used = true
"virtio-pci" "disable-legacy" "off", user_provided = false, used = true
"x86_64-cpu" "cpuid-0xb" "off", user_provided = false, used = true
"vmxnet3" "romfile" "", user_provided = false, used = false
"x86_64-cpu" "fill-mtrr-mask" "off", user_provided = false, used = true
"apic-common" "legacy-instance-id" "on", user_provided = false, used = true
"isa-fdc" "fallback" "144", user_provided = false, used = true
"pvscsi" "x-old-pci-configuration" "on", user_provided = false, used = false
"pvscsi" "x-disable-pcie" "on", user_provided = false, used = false
"vmxnet3" "x-old-msi-offsets" "on", user_provided = false, used = false
"vmxnet3" "x-disable-pcie" "on", user_provided = false, used = false
"virtio-blk-device" "scsi" "true", user_provided = false, used = false
"e1000" "extra_mac_registers" "off", user_provided = false, used = false
"virtio-pci" "x-disable-pcie" "on", user_provided = false, used = true
"virtio-pci" "migrate-extra" "off", user_provided = false, used = true
"fw_cfg_mem" "dma_enabled" "off", user_provided = false, used = false
"fw_cfg_io" "dma_enabled" "off", user_provided = false, used = true
"migration" "send-configuration" "off", user_provided = false, used = true
"migration" "send-section-footer" "off", user_provided = false, used = true
"migration" "store-global-state" "off", user_provided = false, used = true
"qemu32-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.4.0", user_provided = false, used = false
"qemu64-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.4.0", user_provided = false, used = true
"athlon-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.4.0", user_provided = false, used = false
"Haswell-x86_64-cpu" "abm" "off", user_provided = false, used = false
"Haswell-noTSX-x86_64-cpu" "abm" "off", user_provided = false, used = false
"Broadwell-x86_64-cpu" "abm" "off", user_provided = false, used = false
"Broadwell-noTSX-x86_64-cpu" "abm" "off", user_provided = false, used = false
"host-x86_64-cpu" "host-cache-info" "on", user_provided = false, used = false
"x86_64-cpu" "check" "off", user_provided = false, used = true
"qemu64-x86_64-cpu" "sse4a" "on", user_provided = false, used = true
"qemu64-x86_64-cpu" "abm" "on", user_provided = false, used = true
"qemu64-x86_64-cpu" "popcnt" "on", user_provided = false, used = true
"qemu32-x86_64-cpu" "popcnt" "on", user_provided = false, used = false
"Opteron_G2-x86_64-cpu" "rdtscp" "on", user_provided = false, used = false
"Opteron_G3-x86_64-cpu" "rdtscp" "on", user_provided = false, used = false
"Opteron_G4-x86_64-cpu" "rdtscp" "on", user_provided = false, used = false
"Opteron_G5-x86_64-cpu" "rdtscp" "on", user_provided = false, used = false