qemu/docs/system/guest-loader.rst
John Snow 450e0f28a4 docs: remove non-reference uses of single backticks
The single backtick markup in ReST is the "default role". Currently,
Sphinx's default role is called "content". Sphinx suggests you can use
the "Any" role instead to turn any single-backtick enclosed item into a
cross-reference.

This is useful for things like autodoc for Python docstrings, where it's
often nicer to reference other types with `foo` instead of the more
laborious :py:meth:`foo`. It's also useful in multi-domain cases to
easily reference definitions from other Sphinx domains, such as
referencing C code definitions from outside of kerneldoc comments.

Before we do that, though, we'll need to turn all existing usages of the
"content" role to inline verbatim markup wherever it does not correctly
resolve into a cross-refernece by using double backticks instead.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20211004215238.1523082-2-jsnow@redhat.com>
2021-11-08 12:27:23 +04:00

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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.