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

[li guang]

在 2013-05-27一的 13:45 +0200，Igor Mammedov写道：
> 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,

Yep, but I think it's a favor to do cpu online.

> at least I've seen this rationale on LKML when topic was discussed and
> automatic cpu_up on hotplug was rejected. 

Oh, and the reason is?
can you give me a link?

Oh, Igor,
I remember that you said you can give me some your considerations
on the further development of cpu hotplug feature, but I haven't got
them :-)

Thanks!