[Discussion] how to implement external power down for ARM

[Peter Maydell]

On 7 May 2015 at 13:18, Shannon Zhao <zhaoshenglong at huawei.com> wrote:
> On 2015/5/7 20:12, Peter Maydell wrote:
>> On 7 May 2015 at 13:10, Shannon Zhao <zhaoshenglong at huawei.com> wrote:
>>> BTW, IIUC QEMU doesn't support the gracefully reboot support. The reboot
>>> depends on libvirt or other management tools. So the reboot case in
>>> virtualization is firstly poweroff, then start again.
>>
>> I'm not sure what you mean by this -- QEMU supports 'reset this
>> VM' at the machine emulation level, so if we can tell the guest
>> to reboot then it should as part of this process issue the
>> PSCI SYSTEM_RESET command, which QEMU/KVM will then handle
>> to do a reset of the VM.

> Yes, QEMU supports reset, but doesn't support (gracefully) reboot.

Isn't that what this ACPI work is about? Tell the guest to initiate
a graceful reboot, and then the guest will tell QEMU to reboot
the emulated h/w when it's ready.

> And
> reset doesn't depends on the guest, it just restart VM forcefully.
> Reboot likes poweroff and start, while reset likes destroy and start.

I (and QEMU) think there is no visible difference between
poweroff-and-restart and destroy-recreate-and-restart...

-- PMM