1Booting Xen
2===========
3
4Xen follows the zImage protocol defined for 32-bit ARM Linux[1] and the
5Image protocol defined for ARM64 Linux[2].
6
7In both cases the recommendation to boot in HYP/EL2 mode is a strict
8requirement for Xen.
9
10The exceptions to this on 32-bit ARM are as follows:
11
12 Xen does not require the machine type to be passed in r1. This
13 register is ignored (so may be invalid or the actual machine type).
14
15 Xen does not support the ATAG list and requires Device
16 Tree. Therefore r2 must point to the physical address of device tree
17 block (dtb) in system RAM.
18
19 NOTE: although Xen uses the zImage protocol there is no compression
20 actually used. This should be transparent to the bootloader. The
21 zImage protocol should still be used and not the stricter "raw
22 (non-zImage)" protocol described in arm/Booting.
23
24There are no exception on 64-bit ARM.
25
26
27Firmware/bootloader requirements
28--------------------------------
29
30Xen relies on some settings the firmware has to configure in EL3 before starting Xen.
31
32* Xen must be entered in NS EL2 mode
33
34* The bit SCR_EL3.HCE (resp. SCR.HCE for 32-bit ARM) must be set to 1.
35
36
37[1] linux/Documentation/arm/Booting
38Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
39
40[2] linux/Documentation/arm64/booting.txt
41Latest version: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.txt
42