Revision as of 22:09, 13 March 2012

This is a proposal for PC System Flash emulation for on QEMU/KVM.

Flash Hardware

Leverage the pre-existing CFI flash support in qemu/hw/pflash_cfi01.c. (Another option is to use qemu/hw/pflash_cfi02.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.

Known Issues

KVM will not boot if -pflash is used and -bios is not used. KVM currently only functions with this support if code is not attempting to run from the emulated flash. This issue does not affect QEMU.

@@ Line 5: / Line 5: @@
 =Command line interface=
-Currently the -pflash parameter has no use with
+Usage of -bios and -pflash parameters as of pc-1.1:
-an x86 or x86-64 system.  To enable PC system flash, this parameter
-would now be used on x86 & x86-64 systems.
-The -bios and -pflash parameters would both now have a use with qemu/kvm:
+{| class='wikitable' border=1
+! KVM enabled !! -pflash used !! -bios used !! Result
+|-
+|rowspan=3 | <Center>No</Center>
+| <Center>Yes</Center> || <Center>-</Center>
+| -pflash parameter will be loaded as flash image just below 4GB.
-{| class='wikitable' border=1
+'bios.bin' and -bios parameter will be ''ignored''.
-! -bios used !! -pflash used !! Result
 |-
 | <Center>No</Center> || <Center>No</Center>
-| (no change) 'bios.bin' will be loaded as rom image.
+| 'bios.bin' will be used to create a read-only pflash drive.
-No system flash is available.
+A flash device is available, but it is read-only.
 |-
 | <Center>No</Center> || <Center>Yes</Center>
-| ('''changing''') -pflash parameter will be loaded as flash image just below 4GB.
+| -bios parameter will be used to create a read-only pflash drive.
+A flash device is available, but it is read-only.
+|-
+|rowspan=3 | <Center>Yes</Center>
+|| <Center>Yes</Center> || <Center>-</Center>
+| An error message condition:
-'bios.bin' will be ''ignored''.
+PC system firmware (pflash) not available
 |-
-| <Center>Yes</Center> || <Center>No</Center>
+|| <Center>No</Center> || <Center>No</Center>
-| (no change) -bios parameter will be loaded as rom image.
+| 'bios.bin' will be loaded as rom image.
 No system flash is available.
 |-
-| <Center>Yes</Center> || <Center>Yes</Center>
+| <Center>No</Center> || <Center>Yes</Center>
-| ('''changing''') -bios parameter will be loaded as rom image just below 4GB.
+| -bios parameter filename will be loaded as rom image.
--pflash parameter will be loaded as flash image just below the bios rom image.
+No system flash is available.
 |}
 =Known Issues=
 * KVM will not boot if -pflash is used and -bios is not used.  KVM currently only functions with this support if code is not attempting to run from the emulated flash.  This issue does not affect QEMU.