Christoffer Dall christoffer.dall@linaro.org writes:
Hardware Description
The Linux kernel's proper entry point always takes a pointer to an FDT, regardless of the boot mechanism, firmware, and hardware description method. Even on real hardware which only supports ACPI and UEFI, the kernel entry point will still receive a pointer to a simple FDT, generated by the Linux kernel UEFI stub, containing a pointer to the UEFI system table. The kernel can then discover ACPI from the system tables. The presence of ACPI vs. FDT is therefore always itself discoverable, through the FDT.
Therefore, the VM implementation must provide through its UEFI implementation, either:
a complete FDT which describes the entire VM system and will boot mainline kernels driven by device tree alone, or
no FDT. In this case, the VM implementation must provide ACPI, and the OS must be able to locate the ACPI root pointer through the UEFI system table.
Maybe I'm missing something, but should this last bit say "a trivial FDT" instead of "no FDT"? If not, I don't understand the first paragraph :-)
Cheers, mwh