On Thu, Nov 6, 2014 at 3:08 PM, Mark Rutland <mark.rutland at arm.com> wrote: > On Thu, Nov 06, 2014 at 01:56:42AM +0000, Dave Young wrote: >> On 11/03/14 at 07:46pm, Mark Rutland wrote: >> > On Fri, Oct 31, 2014 at 07:52:09AM +0000, Dave Young wrote: >> > > Hi Geoff >> > > >> > > I tested your patches. The macihne is using spin-table cpu enable method >> > > so I tried maxcpus=1 as you suggested. >> > > >> > > There's below issues for me, thoughts? >> > > >> > > 1. For acpi booting there's no /proc/device-tree so kexec can not find dtb >> > > to use. >> > >> > Are you absolutely certain of this? >> > >> > To use ACPI, you must have booted via EFI, as the only mechanism for >> > finding the ACPI tables is via EFI. If booted via EFI, the stub will >> > have created a stub DTB if there is no provided DTB, to pass the command >> > line and pointers to EFI data structures. This stub DTB should be >> > present in the usual place. >> >> Mark, I used kexec-tools from Geoff's git tree, it will create dtb from procfs >> maybe I can pass external dtb to kexec-tools. What you mentioned should be true >> though but I have not get idea how to get the dtb which kernel is using for boot >> since it is not unflattened. > > Ah, sorry. I see the problem now. For ACPI you don't unflatten the tree, > so there's nothing to expose at in sysfs/procfs. > > Somehow we need to unflatten the DTB without exposing it to drivers, > such that it can be exposed to userspace in the usual place but drivers > don't being probing based off of it. Is that even necessary? If the tree isn't unflattened, then it is just a stub tree. There really isn't anything interesting in it. Kexec should recreate the tree from scratch in that case. g.
