[RFC PATCH 2/5] ARM/ARM64: KVM: Forward PSCI SYSTEM_OFF and SYSTEM_RESET to user space

[Peter Maydell]

On 17 October 2013 10:21, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On 17/10/13 10:10, Peter Maydell wrote:
>> On 17 October 2013 09:37, Marc Zyngier <marc.zyngier at arm.com> wrote:
>>> On 16/10/13 18:02, Anup Patel wrote:
>>>> The PSCI SYSTEM_OFF and SYSTEM_RESET functions are VM or Guest level
>>>> functions hence cannot be emulated by the in-kernel PSCI emulation code.
>>>
>>> Why can't we implement system-wide functionality in the kernel? I fail
>>> to see the issue here.
>>
>> Because the kernel isn't emulating the whole board, and you need
>> to power off or reset the whole board, not just the CPUs.
>
> In which case we can forward a generic event, once KVM has dealt with
> the CPUs.

Ideally per-CPU reset should be driven by userspace, incidentally.
We ought to have an ioctl for "hey, reset this CPU': at the moment
we have to fake it up by having QEMU feed the CPU back the register
values it read on powerup, which is kind of ugly.

-- PMM