[qemu.git] / docs / xen-save-devices-state.txt

= Save Devices =

QEMU has code to load/save the state of the guest that it is running.
These are two complementary operations.  Saving the state just does
that, saves the state for each device that the guest is running.

These operations are normally used with migration (see migration.txt),
however it is also possible to save the state of all devices to file,
without saving the RAM or the block devices of the VM.

This operation is called "xen-save-devices-state" (see
qmp-commands.txt)


The binary format used in the file is the following:


-------------------------------------------

32 bit big endian: QEMU_VM_FILE_MAGIC
32 bit big endian: QEMU_VM_FILE_VERSION

for_each_device
{
    8 bit:              QEMU_VM_SECTION_FULL
    32 bit big endian:  section_id
    8 bit:              idstr (ID string) length
    string:             idstr (ID string)
    32 bit big endian:  instance_id
    32 bit big endian:  version_id
    buffer:             device specific data
}

8 bit: QEMU_VM_EOF
Commit	Line	Data
a7ae8355 SS	1	= Save Devices =
	2
	3	QEMU has code to load/save the state of the guest that it is running.
	4	These are two complementary operations. Saving the state just does
	5	that, saves the state for each device that the guest is running.
	6
	7	These operations are normally used with migration (see migration.txt),
	8	however it is also possible to save the state of all devices to file,
	9	without saving the RAM or the block devices of the VM.
	10
	11	This operation is called "xen-save-devices-state" (see
fd11080b	12	qmp-commands.txt)
a7ae8355 SS	13
	14
	15	The binary format used in the file is the following:
	16
	17
	18	-------------------------------------------
	19
	20	32 bit big endian: QEMU_VM_FILE_MAGIC
	21	32 bit big endian: QEMU_VM_FILE_VERSION
	22
	23	for_each_device
	24	{
	25	8 bit: QEMU_VM_SECTION_FULL
	26	32 bit big endian: section_id
	27	8 bit: idstr (ID string) length
	28	string: idstr (ID string)
	29	32 bit big endian: instance_id
	30	32 bit big endian: version_id
	31	buffer: device specific data
	32	}
	33
	34	8 bit: QEMU_VM_EOF