Re: [PATCH v2 6/7] docs: add some documentation for the guest-loader

[Alistair Francis <alistair23@xxxxxxxxx>]

On Thu, Feb 11, 2021 at 9:20 AM Alex Bennée <alex.bennee@xxxxxxxxxx> wrote:
>
> Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
> Message-Id: <20201105175153.30489-7-alex.bennee@xxxxxxxxxx>

Reviewed-by: Alistair Francis <alistair.francis@xxxxxxx>

Alistair

>
> ---
> v2
>   - add docs and MAINTAINERS
> ---
>  docs/system/guest-loader.rst | 54 ++++++++++++++++++++++++++++++++++++
>  docs/system/index.rst        |  1 +
>  MAINTAINERS                  |  1 +
>  3 files changed, 56 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
> +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
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 774b3ca7a5..853f174fcf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1997,6 +1997,7 @@ Guest Loader
>  M: Alex Bennée <alex.bennee@xxxxxxxxxx>
>  S: Maintained
>  F: hw/core/guest-loader.c
> +F: docs/system/guest-loader.rst
>
>  Intel Hexadecimal Object File Loader
>  M: Su Hang <suhang16@xxxxxxxxxxxxxxxx>
> --
> 2.20.1
>
>