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

[Christoffer Dall]

On Wed, Dec 18, 2013 at 03:41:27PM +0000, Marc Zyngier wrote:
> Hi Anup,
> 
> On Wed, Dec 18 2013 at 03:03:43 PM, Anup Patel <anup at brainfault.org> wrote:
> > On Wed, Dec 18, 2013 at 8:08 PM, Marc Zyngier <marc.zyngier at arm.com> 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).
> >
> > Should we emulate PSCI_VERSION call to help Guest determine
> > the spec version emulated by KVM (i.e. v0.1 or v0.2) ??
> 
> I think that'd be a nice to have, but the guest is likely to get its
> information from the DT anyway. Plus I don't think the original PSCI
> spec specified PSCI_VERSION, which only make it useful for whatever
> comes after v0.2.
> 
> So I think we need to:
> - Use the new range for PSCI v0.2 (while still supporting v0.1 and the
> old range)
> - Get the kernel and DT bindings into shape
> - Merge all of that at the same time
> 
Don't we also need a way for user space to tell KVM if it should emulate
v0.1 or v0.2 of PSCI so we don't break backwards compatibility with
tools that spit out a device tree and use guest kernels based on v0.1?

This could be a new feature for KVM_ARM_VCPU_INIT, but perhaps it should
be something on the VM level, hmmm.

-Christoffer