55 lines
1.9 KiB
ReStructuredText
55 lines
1.9 KiB
ReStructuredText
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Copyright (c) 2020, Linaro
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Guest Loader
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------------
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The guest loader is similar to the `generic-loader` although it is
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aimed at a particular use case of loading hypervisor guests. This is
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useful for debugging hypervisors without having to jump through the
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hoops of firmware and boot-loaders.
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The guest loader does two things:
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- load blobs (kernels and initial ram disks) into memory
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- sets platform FDT data so hypervisors can find and boot them
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This is what is typically done by a boot-loader like grub using it's
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multi-boot capability. A typical example would look like:
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.. parsed-literal::
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|qemu_system| -kernel ~/xen.git/xen/xen \
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-append "dom0_mem=1G,max:1G loglvl=all guest_loglvl=all" \
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-device guest-loader,addr=0x42000000,kernel=Image,bootargs="root=/dev/sda2 ro console=hvc0 earlyprintk=xen" \
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-device guest-loader,addr=0x47000000,initrd=rootfs.cpio
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In the above example the Xen hypervisor is loaded by the -kernel
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parameter and passed it's boot arguments via -append. The Dom0 guest
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is loaded into the areas of memory. Each blob will get
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`/chosen/module@<addr>` entry in the FDT to indicate it's location and
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size. Additional information can be passed with by using additional
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arguments.
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Currently the only supported machines which use FDT data to boot are
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the ARM and RiscV `virt` machines.
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Arguments
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^^^^^^^^^
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The full syntax of the guest-loader is::
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-device guest-loader,addr=<addr>[,kernel=<file>,[bootargs=<args>]][,initrd=<file>]
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``addr=<addr>``
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This is mandatory and indicates the start address of the blob.
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``kernel|initrd=<file>``
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Indicates the filename of the kernel or initrd blob. Both blobs will
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have the "multiboot,module" compatibility string as well as
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"multiboot,kernel" or "multiboot,ramdisk" as appropriate.
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``bootargs=<args>``
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This is an optional field for kernel blobs which will pass command
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like via the `/chosen/module@<addr>/bootargs` node.
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