[PATCH 0/8] arm64 kexec kernel patches V7

[Catalin Marinas]

Hi Geoff,

On Sat, Jan 17, 2015 at 12:23:34AM +0000, Geoff Levand wrote:
> This series adds the core support for kexec re-boots on arm64.  This v7 of the
> series is mainly just a rebase to the latest arm64 for-next/core branch
> (v3.19-rc4), and a few very minor changes requested for v6.

I haven't looked at the series in detail before, so some of my comments
may have already been discussed.

> Several things are known to have problems on kexec re-boot:
> 
> spin-table

I think that's not too bad, for complete kexec support (SMP->SMP) we can
require some CPU unplug mechanism and PSCI is one of them.

> FIX: Upgrade system firmware to provide PSCI enable method support or add
> missing spin-table support to the kernel.

What's the missing spin-table support?

> ACPI
> ----
> 
> PROBLEM: The kernel for ACPI based systems does not export a device tree to the
> standard user space location of 'proc/device-tree'.  Current applications
> expect to access device tree information from this standard location.
> 
> WORK-AROUND: Disable ACPI in firmware, OR pass 'acpi=off' on the first stage
> kernel command line, OR pass a user specified DTB using the kexec --dtb option.
> 
> FIX: FIX: An interface to expose a binary device tree to user space has been
> proposed.  User kexec utilities will need to be updated to add support for this
> new interface.

So the fix here is to boot the second stage kernel with dtb, which means
that we mandate the existence of a DT file for any ACPI system. Are
there plans to make the kexec'ed kernel reuse the ACPI tables?

-- 
Catalin