PC System Flash emulation was added for QEMU in pc-1.1. It is currently not supported by KVM.

Flash Hardware

Uses CFI flash support in hw/pflash_cfi01.c.

Command line interface

Usage of -bios and -pflash parameters as of pc-1.1:

KVM enabled	-pflash used	-bios used	Result
No	Yes	-	-pflash parameter will be loaded as flash image just below 4GB. 'bios.bin' and -bios parameter will be ignored.
	No	No	'bios.bin' will be used to create a read-only pflash drive. A flash device is available, but it is read-only.
	No	Yes	-bios parameter will be used to create a read-only pflash drive. A flash device is available, but it is read-only.
Yes	Yes	-	An error message condition: PC system firmware (pflash) not available
	No	No	'bios.bin' will be loaded as rom image. No system flash is available.
	No	Yes	-bios parameter filename will be loaded as rom image. No system flash is available.

KVM support is being investigated, but it will require modification of KVM (kernel + qemu) to enable KVM read-only page support.