[PATCH v3 0/2] PSCI system off and reset for KVM ARM/ARM64

[Marc Zyngier]

Hi Rob,

On Wed, Dec 18 2013 at 03:42:09 PM, Rob Herring <robherring2 at gmail.com> wrote:
> Adding Mark Rutland.
>
> On 12/18/2013 08:38 AM, Marc Zyngier wrote:
>> Christoffer Dall <christoffer.dall at linaro.org> writes:
>> 
>>> On Tue, Dec 17, 2013 at 05:05:34PM +0530, Anup Patel wrote:
>>>> The Power State and Coordination Interface (PSCI) specification defines
>>>> SYSTEM_OFF and SYSTEM_RESET functions for system poweroff and reboot.
>>>>
>>>> This patchset adds emulation of PSCI SYSTEM_OFF and SYSTEM_RESET functions
>>>> in KVM ARM/ARM64 by forwarding them to user space (QEMU or KVMTOOL) using
>>>> KVM_EXIT_SYSTEM_EVENT exit reason.
>>>>
>>>> To try this patch from guest kernel, we will need PSCI-based restart and
>>>> poweroff support in the guest kenel for both ARM and ARM64.
>>>>
>>>> Rob Herring has already submitted patches for PSCI-based restart and
>>>> poweroff in ARM kernel but these are not merged yet due unstable device
>>>> tree bindings of kernel PSCI support. We will be having similar patches
>>>> for PSCI-based restart and poweroff in ARM64 kernel.
>>>> (Refer http://www.spinics.net/lists/arm-kernel/msg262217.html)
>>>> (Refer http://www.spinics.net/lists/devicetree/msg05348.html)
>>>
>>> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
>>>
>>> I can merge this series if Marc acks it as well.
>> 
>> The patches themselves are mostly fine. One issue though: They implement
>> part of the v0.2 spec, but keep on using the range of function IDs that
>> we made up for v0.1.
>> 
>> I just had a chat with the person responsible for the spec, and realized
>> that the Function IDs mentionned in the v0.2 spec are not optional, and
>> not using them would be in direct violation of the spec (the new numbers
>> now come directly from the SMC calling convention).
>
> News to me. That is exactly the opposite of what Mark Rutland told me.
> This would certainly simplify things since the SMC calling convention
> IDs encode the size and there would be no reason to put the IDs into
> DT.

Hmmm. I'd hate to contredict Mark. But as he's on holiday (and hopefully
unlikely to reply immediately), I win the argument! ;-)

More seriously, given that we have a document specifying the IDs, I'd be
inclined to follow it. It is not that often that ARM actually *mandates*
something... ;-)

Mark (assuming you're reading this): what were your objections about
following the ID mentioned in the spec?

>> So I rekon we need to create a separate range for those. Also, I'd like
>> to progress the DT and kernel side of things as well (otherwise this is
>> all a bit pointless).
>> 
>> Rob: what are your plans regarding your PSCI v0.2 patches?
>
> My plan was to simply add 2 optional properties for reset/off and be
> done with it like is done here. I'll leave it to ARM to sort out all of
> v0.2 ID and 32-bit vs. 64-bit issues.

Thankfully, RESET and OFF are not of those property with two IDs.

Thanks,

        M.
-- 
Jazz is not dead. It just smells funny.