On Wed, Nov 12, 2014 at 11:07:22AM +0000, Mark Rutland wrote: > [...] > > > > > > > We are currently suggesting adding an RDSP property to the chosen > > > > > > node > > > > > > in the tiny DT, but a command-line arguement like kexec proposed > > > > > > could > > > > > > be another option I guess, albeit not a very pretty one. > > > > > > > > > > I'm not sure what an RDSP command line property would have to do with > > > > > kexec. I'll assume I've misunderstood something. > > > > > > > > > > > > > I thought the kexec patches proposed passing the RDSP on the > > > > command-line to boot the secondary kernel, so if that ended up being > > > > supported by the kernel for kexec, maybe that could be leveraged by > > > > Xen's boot protocol. It was an idea someone brought to me, just thought > > > > I'd mention it. > > > > > > Ah, that's not something I'd heard of. > > > > Maybe there was a misunderstanding then, I thought you were cc'ed on > > those discussions. > > I may just have lost them in my inbox. I'm on a few too many mailing > lists these days. Sorry about that. > > > > I'm not a fan of placing fundamentally required system description on > > > the command line. It's fine for explicit overrides but I don't think it > > > should be the default mechanism as that causes its own set of problems > > > (who wants to fight with their hypervisor to pass a command line to a > > > guest kernel?). > > > > > > > Agreed completely, but I've been lacking strong technical arguments > > against passing this stuff on the cmdline. My personal preferred > > approach for the Xen Dom0 case is to add a property to the DT. > > Something under /chosen, or a firmware node would sound preferable to > me. For UEFI we pass the system table address as > /chosen/linux,uefi-system-table = <... ...>, and I think the RDSP could > be handled similarly if necessary. The user can than override that via > the command line if desired. > We have actually done that in the past when we had to support u-boot and bootwrapper as a bootloader. It works fine in the kernel and its a minimal patch to support.
Graeme