Signed-off-by: Alex Bennée alex.bennee@linaro.org Reviewed-by: Alistair Francis alistair.francis@wdc.com Message-Id: 20201105175153.30489-7-alex.bennee@linaro.org Message-Id: 20210211171945.18313-7-alex.bennee@linaro.org --- 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 34cdd20672..8ec6fbc259 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2011,6 +2011,7 @@ Guest Loader M: Alex Bennée alex.bennee@linaro.org S: Maintained F: hw/core/guest-loader.c +F: docs/system/guest-loader.rst
Intel Hexadecimal Object File Loader M: Su Hang suhang16@mails.ucas.ac.cn