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authorAlex Bennée2021-03-03 18:36:41 +0100
committerAlex Bennée2021-03-10 16:34:11 +0100
commit0146037807831ff6424e5b8be66532ce39f0eb13 (patch)
treed0277537480bde8e4d53599ef56f16e0022445c9 /docs/system
parentdocs: move generic-loader documentation into the main manual (diff)
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docs: add some documentation for the guest-loader
Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Message-Id: <20210303173642.3805-7-alex.bennee@linaro.org>
Diffstat (limited to 'docs/system')
-rw-r--r--docs/system/guest-loader.rst54
-rw-r--r--docs/system/index.rst1
2 files changed, 55 insertions, 0 deletions
diff --git a/docs/system/guest-loader.rst b/docs/system/guest-loader.rst
new file mode 100644
index 0000000000..37d03cbd89
--- /dev/null
+++ b/docs/system/guest-loader.rst
@@ -0,0 +1,54 @@
+..
+ Copyright (c) 2020, Linaro
+
+Guest Loader
+------------
+
+The guest loader is similar to the `generic-loader` although it is
+aimed at a particular use case of loading hypervisor guests. This is
+useful for debugging hypervisors without having to jump through the
+hoops of firmware and boot-loaders.
+
+The guest loader does two things:
+
+ - load blobs (kernels and initial ram disks) into memory
+ - sets platform FDT data so hypervisors can find and boot them
+
+This is what is typically done by a boot-loader like grub using it's
+multi-boot capability. A typical example would look like:
+
+.. parsed-literal::
+
+ |qemu_system| -kernel ~/xen.git/xen/xen \
+ -append "dom0_mem=1G,max:1G loglvl=all guest_loglvl=all" \
+ -device guest-loader,addr=0x42000000,kernel=Image,bootargs="root=/dev/sda2 ro console=hvc0 earlyprintk=xen" \
+ -device guest-loader,addr=0x47000000,initrd=rootfs.cpio
+
+In the above example the Xen hypervisor is loaded by the -kernel
+parameter and passed it's boot arguments via -append. The Dom0 guest
+is loaded into the areas of memory. Each blob will get
+`/chosen/module@<addr>` entry in the FDT to indicate it's location and
+size. Additional information can be passed with by using additional
+arguments.
+
+Currently the only supported machines which use FDT data to boot are
+the ARM and RiscV `virt` machines.
+
+Arguments
+^^^^^^^^^
+
+The full syntax of the guest-loader is::
+
+ -device guest-loader,addr=<addr>[,kernel=<file>,[bootargs=<args>]][,initrd=<file>]
+
+``addr=<addr>``
+ This is mandatory and indicates the start address of the blob.
+
+``kernel|initrd=<file>``
+ Indicates the filename of the kernel or initrd blob. Both blobs will
+ have the "multiboot,module" compatibility string as well as
+ "multiboot,kernel" or "multiboot,ramdisk" as appropriate.
+
+``bootargs=<args>``
+ This is an optional field for kernel blobs which will pass command
+ like via the `/chosen/module@<addr>/bootargs` node.
diff --git a/docs/system/index.rst b/docs/system/index.rst
index cee1c83540..6ad9c93806 100644
--- a/docs/system/index.rst
+++ b/docs/system/index.rst
@@ -26,6 +26,7 @@ Contents:
ivshmem
linuxboot
generic-loader
+ guest-loader
vnc-security
tls
gdb