Re: [Qemu-devel] [PATCH RFC v2 0/7] coordinate cpu hotplug/unplug bewteen QEMU and kernel by EC

[li guang]

Hi, Igor and Micheal

在 2013-06-06四的 16:33 +0800，li guang写道：
> 在 2013-06-06四的 11:13 +0300，Michael S. Tsirkin写道：
> > On Thu, Jun 06, 2013 at 11:16:53AM +0800, liguang wrote:
> > > v2: 
> > > 1.remove PIIX4_PROC_BASE operations for cpu hotplug
> > > 2.fix wrong description fo cpu-del
> > > 
> > > patch 1 adds ACPI Embedded Controller (EC),
> > > refer-to:
> > > ACPI SPEC v5 chapter 12
> > > "ACPI Embedded Controller Interface Specification"
> > > 
> > > EC is a standard ACPI device, it plays flexible roles,
> > > especially be event carrier, it can pass events between platform
> > > and OS, so OS can execute _Qxx method which defined
> > > by yourself and query EC's ACPI space which can be a buffer for
> > > many purposes
> > > 
> > > here, 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' and also for offline to do real cpu
> > > removal.
> > 
> > So, it's another channel to the guest.
> > Can't qemu-ga do this in userspace, using the existing channel?
> 
> Sorry, I'm not familiar with qemu-ga,
> anyway, maybe we don't want to do things like
> 'exec("echo 1 > /sys/devices/system/cpu/cpu1/online")'
> in userspace.
> 
> BTW, Michael,
> do you think if we use EC space to pass info between
> platform(QEMU) and OS(PM) instead of 'PIIX4_PROC_BASE' and
> something like it can bring some convenience?
> for we can directly operate on EC space, we don't have to
> register memory regions and ops for them any more, and also,
> these regions are mostly not exist in real platforms,
> this a motivation that I add this device.
> 

does this approach have some benefit?

> > 
> > > what I am trying to do is emulated physical addition/removal
> > > (like described by linux kernel document for cpu hotplug --
> > > linux-2.6/Documentation/cpu-hotplug.txt) for QEMU.
> > > 
> > > these RFC patches are sent for demo what I am trying to do.
> > > 
> > > the design process simply like following:
> > > 
> > > hotplug
> > > qemu::ec::sci -> kernel::ec::gpe::notifier->
> > > kernel::cpu_physic_hotplug::handler->kernel::cpu_up
> > > 
> > > unplug
> > > kernel::cpu_down::kernel::cpu_physic_hotplug::handler->
> > > kernel::ec::ec_write->qemu::ec::->qemu::cpu-unplug
> > > 
> > > sorry, I should poll cpu-unplug cmd sent from kernel,
> > > but, it's a little trivial, I want do it later.
> > > 
> > > for kernel patches:
> > > http://comments.gmane.org/gmane.linux.kernel/1503460
> > > 
> > > 
> > > Li Guang (8)
> > >    acpi: add ACPI Embedded Controller support
> > >    ich9: add notifer for ec to generate sci
> > >    ec: add operations for _Qxx events
> > >    piix4: add notifer for ec to generate sci
> > >    piix4: add events for cpu hotplug
> > >    qmp: add 'cpu-del' command
> > >    pc: add EC qdev init for piix & q35
> > >    cpu-hotplug: remove memory regison for cpu hotplug
> > > 
> > > default-configs/x86_64-softmmu.mak |   1 +
> > > hw/acpi/Makefile.objs              |   1 +
> > > hw/acpi/ec.c                       | 225 
> > > ++++++++++++++++++++++++++++++++++++
> > > hw/acpi/ich9.c                     |  15 +++++++++++++++
> > > hw/acpi/piix4.c                    |  68 ++++++++++++++
> > > hw/i386/pc.c                       |  46 ++++++++++++++++++++++++++++--
> > > hw/i386/pc_piix.c                  |   7 +
> > > hw/i386/pc_q35.c                   |   6 +
> > > include/hw/acpi/ec.h               |  44 ++++++
> > > include/hw/acpi/ich9.h             |   1 +
> > > include/hw/boards.h                |   5 +++--
> > > include/hw/i386/pc.h               |   1 +
> > > qapi-schema.json                   |  13 +++++++++++++
> > > qmp-commands.hx                    |  23 +++++++++++++++++++++++
> > > qmp.c                              |   9 +++++++++
> > > 15 files changed, 411 insertions(+), 54 deletions(-)
> > >  create mode 100644 hw/acpi/ec.c
> > >  create mode 100644 include/hw/acpi/ec.h
> 
> 
>