Re: [Qemu-devel] [PATCH 0/4] add ACPI Embedded Controller

[Igor Mammedov]

On Mon, 27 May 2013 09:22:59 +0800
li guang <address@hidden> wrote:

> 在 2013-05-26日的 19:51 -0500，Anthony Liguori写道：
> > li guang <address@hidden> writes:
> > 
> > > 在 2013-05-24五的 14:45 +0300，Michael S. Tsirkin写道：
> > >> On Wed, May 22, 2013 at 11:46:33AM +0800, liguang wrote:
> > >> > These patches try to add ACPI Embedded Controller (EC),
> > >> > refer-to:
> > >> > ACPI SPEC v5 chapter 5 
> > >> > "ACPI Embedded Controller Interface Specification"
> > >> > 
> > >> > EC is a standard ACPI device, it plays flexible roles,
> > >> > e.g. 
> > >> > power controller, it can control power sequence for
> > >> > platform to enter or leave system state(0,1,3,4,5),
> > >> > it can controller CPU fan by the temperature of sensor.
> > >> > event carrier, it can pass events between platform
> > >> > and OS, so OS can execute _Qxx method which defined
> > >> > by yourself.
> > >> > 
> > >> > So, I want to deliver CPU online/offline event between
> > >> > OS and QEMU for CPU hotplug feature, then we will don't
> > >> > need to "echo 1 > /sys/devices/system/cpu/cpu1/online"
> > >> > again after 'cpu-add'.
> > >> > 
> > >> > patches for online/offline event handler of QEUM and 
> > >> > linux kernel are writing, and will send once finished.
> > >> > 
> > >> > since EC is a common device, so I send pathes separately.
> > >> 
> > >> Do any non-linux guests support this device?
> > >> 
> > >
> > > In fact, any OSes support ACPI will support this device.
> > > so, windows will.
> > 
> > When you say "any OSes supporting ACPI" I think what you really mean is
> > that we can provide bytecode that interacts with the embedded
> > controller.
> > 
> > There is not explicit driver in Linux or Windows AFAIK.
> 
> Hmm, yep, mostly there's no special driver for EC,
> because it is directly embedded in code for ACPI
> for linux kernel, it's drivers/acpi/ec.c
> 
> > 
> > I still don't get the point of this.  We can make ACPI hotplug work
> > without introducing a new device like this.
> > 
> 
> when you 'cpu-add' a cpu, acpi driver for cpu will not
> trigger 'cpu_up' for linux kernel AFAIK, unless you add
> a user space program to listen it's uevent and tigger 'cpu_up'.
it is up to guest OS policy to decide if CPU should be onlined or not,
at least I've seen this rationale on LKML when topic was discussed and
automatic cpu_up on hotplug was rejected.