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1 | .. |
2 | Copyright (c) 2020, Linaro | |
3 | ||
4 | Guest Loader | |
5 | ------------ | |
6 | ||
6df743dc | 7 | The guest loader is similar to the ``generic-loader`` although it is |
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8 | aimed at a particular use case of loading hypervisor guests. This is |
9 | useful for debugging hypervisors without having to jump through the | |
10 | hoops of firmware and boot-loaders. | |
11 | ||
12 | The guest loader does two things: | |
13 | ||
14 | - load blobs (kernels and initial ram disks) into memory | |
15 | - sets platform FDT data so hypervisors can find and boot them | |
16 | ||
d035fb10 | 17 | This is what is typically done by a boot-loader like grub using its |
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18 | multi-boot capability. A typical example would look like: |
19 | ||
20 | .. parsed-literal:: | |
21 | ||
22 | |qemu_system| -kernel ~/xen.git/xen/xen \ | |
23 | -append "dom0_mem=1G,max:1G loglvl=all guest_loglvl=all" \ | |
24 | -device guest-loader,addr=0x42000000,kernel=Image,bootargs="root=/dev/sda2 ro console=hvc0 earlyprintk=xen" \ | |
25 | -device guest-loader,addr=0x47000000,initrd=rootfs.cpio | |
26 | ||
27 | In the above example the Xen hypervisor is loaded by the -kernel | |
d035fb10 | 28 | parameter and passed its boot arguments via -append. The Dom0 guest |
01460378 | 29 | is loaded into the areas of memory. Each blob will get |
d035fb10 | 30 | ``/chosen/module@<addr>`` entry in the FDT to indicate its location and |
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31 | size. Additional information can be passed with by using additional |
32 | arguments. | |
33 | ||
34 | Currently the only supported machines which use FDT data to boot are | |
6df743dc | 35 | the ARM and RiscV ``virt`` machines. |
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36 | |
37 | Arguments | |
38 | ^^^^^^^^^ | |
39 | ||
40 | The full syntax of the guest-loader is:: | |
41 | ||
42 | -device guest-loader,addr=<addr>[,kernel=<file>,[bootargs=<args>]][,initrd=<file>] | |
43 | ||
44 | ``addr=<addr>`` | |
45 | This is mandatory and indicates the start address of the blob. | |
46 | ||
47 | ``kernel|initrd=<file>`` | |
48 | Indicates the filename of the kernel or initrd blob. Both blobs will | |
49 | have the "multiboot,module" compatibility string as well as | |
50 | "multiboot,kernel" or "multiboot,ramdisk" as appropriate. | |
51 | ||
52 | ``bootargs=<args>`` | |
53 | This is an optional field for kernel blobs which will pass command | |
450e0f28 | 54 | like via the ``/chosen/module@<addr>/bootargs`` node. |