docs/devel/s390-dasd-ipl.rst

1 Booting from real channel-attached devices on s390x
5 -----------------
18    IPL ccw it read the 24-bytes of IPL1 to be read into memory starting at
22    and the TIC (Transfer In Channel) will transfer control to the channel
30    the execution of the IPL2 channel program. IPL2 is stage-2 of the boot
32    IPL2 is to find and load either the operating system or a small program that
33    loads the operating system from disk. At the end of this step all or some of
34    the real operating system is loaded into memory and we are ready to hand
35    control over to the guest operating system. At this point the guest
36    operating system is entirely responsible for loading any more data it might
42    address points to the guest operating system code to execute at the end of
47 4. Start executing the guest operating system.
49    should contain the needed flags for the operating system we have loaded. The
51    to start executing the operating system. This psw is loaded (via LPSW
52    instruction) causing control to be passed to the operating system code.
54 In a non-virtualized environment this process, handled entirely by the hardware,
66 ----------------------------------------------
69 operating system from a DASD device:
77 non-prefetch of ccw data.
81 bit is on then the vfio-ccw kernel driver is allowed to read the entire channel
85 the kernel's channel subsystem memory. The kernel vfio-ccw driver currently
87 the IPL process consists of transferring control from the "Read IPL" ccw
91 IPL1 channel program from transferring control to the IPL2 channel program.
94 transfers control to another channel program segment immediately after reading
98 --------------
125    by turning off the chain bit in the READ ccw. When control is returned from
132    Now the operating system code is loaded somewhere in guest memory and the psw
134    system.
138    LPSW transfers control to the guest operating system and we're done.