[PATCH 00/10] arm64 kexec kernel patches V5

Grant Likely grant.likely at linaro.org
Thu Nov 6 16:41:45 PST 2014

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.


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