On Fri, Nov 07, 2014 at 12:41:45AM +0000, Grant Likely wrote: > 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. We need to UEFI properties [1] from /chosen to access the memory map and system table (both of which are necessary to access any ACPI tables). > Kexec should recreate the tree from scratch in that case. I'm not sure if the required information is exposed to userspace elsewhere. Ard, Leif? Mark. [1] Documentation/arm/uefi.txt
