ChangeLog/2.9
System emulation
Incompatible changes
Future incompatible changes
ARM
KVM
MIPS
PowerPC
pSeries
s390
SH
SPARC
TileGX
Tricore
x86
Xen
SMI broadcast
The pc-q35-2.9 machine type now offers SMI feature negotiation to interested guest firmware. The negotiation interface resembles virtio-1.0, with the etc/smi/supported-features, etc/smi/requested-features, and etc/smi/features-ok fw_cfg files. Currently one bit can be negotiated by guest firmware, ICH9_LPC_SMI_F_BROADCAST_BIT, which causes QEMU to inject a syncronous SMI (triggered through APM_CNT_IOPORT) on all VCPUs at once. This benefits the edk2 SMM driver stack as built into OVMF.
Device emulation and assignment
ACPI
Block devices
Network devices
SCSI
PCI/PCIe
USB
VFIO
virtio
Xen
fw_cfg
The DMA interface to fw_cfg now supports writeable blobs.
The fw_cfg_io and fw_cfg_mem devices now have more slots for files; the FW_CFG_FILE_SLOTS constant has been replaced with the (internal only) x-file-slots property. The property can be further raised in future machine types if absolutely necessary.