docs/devel/s390-dasd-ipl.rst

1 Booting from real channel-attached devices on s390x
4 s390 hardware IPL
5 -----------------
7 The s390 hardware IPL process consists of the following steps.
9 1. A READ IPL ccw is constructed in memory location ``0x0``.
10    This ccw, by definition, reads the IPL1 record which is located on the disk
11    at cylinder 0 track 0 record 1. Note that the chain flag is on in this ccw
12    so when it is complete another ccw will be fetched and executed from memory
15 2. Execute the Read IPL ccw at ``0x00``, thereby reading IPL1 data into ``0x00``.
17    information: ``[psw][read ccw][tic ccw]``. When the machine executes the Read
18    IPL ccw it read the 24-bytes of IPL1 to be read into memory starting at
19    location ``0x0``. Then the ccw program at ``0x08`` which consists of a read
20    ccw and a tic ccw is automatically executed because of the chain flag from
21    the original READ IPL ccw. The read ccw will read the IPL2 data into memory
29    The TIC ccw instruction at the end of the IPL1 channel program will begin
30    the execution of the IPL2 channel program. IPL2 is stage-2 of the boot
54 In a non-virtualized environment this process, handled entirely by the hardware,
56 management console. This "Load" procedure crafts a special "Read IPL" ccw in
57 memory location 0x0 that reads IPL1. It then executes this ccw thereby kicking
59 written immediately after the special "Read IPL" ccw, the IPL1 channel program
60 will be executed immediately (the special read ccw has the chaining bit turned
66 ----------------------------------------------
71 1. Place a "Read IPL" ccw into memory location ``0x0`` with chaining bit on.
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
98 --------------
104 1. Place "Read IPL" ccw into memory location ``0x0``, but turn off chaining bit.
124    that detects a READ immediately followed by a TIC and breaks the ccw chain
125    by turning off the chain bit in the READ ccw. When control is returned from