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[RFC PATCH 06/15] docs: add some documentation for the guest-loader

From: Alex Bennée
Subject: [RFC PATCH 06/15] docs: add some documentation for the guest-loader
Date: Thu, 5 Nov 2020 17:51:44 +0000

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
 docs/system/guest-loader.rst | 54 ++++++++++++++++++++++++++++++++++++
 docs/system/index.rst        |  1 +
 2 files changed, 55 insertions(+)
 create mode 100644 docs/system/guest-loader.rst

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
+Currently the only supported machines which use FDT data to boot are
+the ARM and RiscV `virt` machines.
+The full syntax of the guest-loader is::
+  -device 
+  This is mandatory and indicates the start address of the blob.
+  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.
+  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 3cff0ca98f..b5cfe8ee93 100644
--- a/docs/system/index.rst
+++ b/docs/system/index.rst
@@ -25,6 +25,7 @@ Contents:
+   guest-loader

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