Kexec on arm64

[achandran@mvista.com (Arun Chandran)]

On Fri, Jul 25, 2014 at 5:47 AM, Geoff Levand <geoff@infradead.org> wrote:
> Hi,
>
> On Thu, 2014-07-24 at 10:36 +0100, Mark Rutland wrote:
>> On Thu, Jul 24, 2014 at 01:38:07AM +0100, Geoff Levand wrote:
>
>> > All memory management for the main cpu is done by the arch code.  Kexec
>> > and cpu hot plug only work with the secondary cpus, so the problem would
>> > be in the arch memory code, either in setup_restart() for shutdown, or
>> > in the startup code.
>>
>> It's possible that soft_restart and setup_restart are a little dodgy, as
>> they also rely on the compiler being smart and not touching the stack
>> after setup_restart().
>>
>> However, they provide absolutely no guarantee that any data has been
>> flushed out to the PoC [1]. If you require any data to be flushed out to the
>> PoC so as to be visible to noncacheable accesses, you will need to
>> ensure that this is flushed by VA before soft_restart is called. Data
>> may have migrated to another cache (e.g. another CPU, or the L3) where
>> it is not visible.
>
> OK, kexec's reset routine relocate_new_kernel does use a few global
> variables that are set by the main kexec routines.  I added a call to
> __flush_dcache_area(), which uses 'dc civac' for those.
>
> I had thought the call to __flush_dcache_all, which uses 'dc cisw', in
> flush_cache_all() would be enough.
>
> Arun, I also fixed UP builds.  Could you pull my latest and try with L3
> enabled?

I tried it but kexeced kernel fails to boot.
Ran the code with and without the call to cpu_cache_off();
in arch/arm64/kernel/process.c. I have put more details
in another mail. Please see that.

--Arun









>
> -Geoff
>