On Wed, Jul 13, 2016 at 10:36:14AM +0800, Dave Young wrote: > But consider we can kexec to a different kernel and a different initrd so there > will be use cases to pass a total different dtb as well. It depends on what you mean by "a different kernel", and what this implies for the DTB. I expect future arm64 Linux kernels to function with today's DTBs, and the existing boot protocol. The kexec_file_load syscall already has enough information for the kernel to inject the initrd and bootargs properties into a DTB. In practice on x86 today, kexec_file_load only supports booting to a Linux kernel, because the in-kernel purgatory only implements the x86 Linux boot protocol. Analagously, for arm64 I think that the first kernel should use its internal copy of the boot DTB, with /chosen fixed up appropriately, assuming the next kernel is an arm64 Linux image. If booting another OS, the only parts of the DTB I would expect to change are the properties under chosen, as everything else *should* be OS-independent. However the other OS may have a completely different boot protocol, might not even take a DTB, and will likely need a compeltely different purgatory implementation. So just allowing the DTB to be altered isn't sufficient for that case. There might be cases where we want a different DTB, but as far as I can tell we have nothing analagous on x86 today. If we do need this, we should have an idea of what real case(s) were trying to solve. Thanks, Mark.
