Re: [Qemu-devel] [PULL 37/47] nvdimm acpi: introduce fit buffer

[Xiao Guangrong]

On 10/31/2016 05:45 PM, Igor Mammedov wrote:
> On Sun, 30 Oct 2016 23:25:05 +0200
> "Michael S. Tsirkin" <address@hidden> wrote:
>
> > From: Xiao Guangrong <address@hidden>
> >
> > The buffer is used to save the FIT info for all the presented nvdimm
> > devices which is updated after the nvdimm device is plugged or
> > unplugged. In the later patch, it will be used to construct NVDIMM
> > ACPI _FIT method which reflects the presented nvdimm devices after
> > nvdimm hotplug
> >
> > As FIT buffer can not completely mapped into guest address space,
> > OSPM will exit to QEMU multiple times, however, there is the race
> > condition - FIT may be changed during these multiple exits, so that
> > some rules are introduced:
> > 1) the user should hold the @lock to access the buffer and
> > 2) mark @dirty whenever the buffer is updated.
> >
> > @dirty is cleared for the first time OSPM gets fit buffer, if
> > dirty is detected in the later access, OSPM will restart the
> > access
> >
> > As fit should be updated after nvdimm device is successfully realized
> > so that a new hotplug callback, post_hotplug, is introduced
> >
> > Signed-off-by: Xiao Guangrong <address@hidden>
> > Reviewed-by: Michael S. Tsirkin <address@hidden>
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> >  include/hw/hotplug.h    | 10 +++++++++
> >  include/hw/mem/nvdimm.h | 26 +++++++++++++++++++++-
> >  hw/acpi/nvdimm.c        | 59 +++++++++++++++++++++++++++++++++++--------------
> >  hw/core/hotplug.c       | 11 +++++++++
> >  hw/core/qdev.c          | 20 +++++++++++++----
> >  hw/i386/acpi-build.c    |  2 +-
> >  hw/i386/pc.c            | 19 ++++++++++++++++
> >  7 files changed, 124 insertions(+), 23 deletions(-)
> >
> > diff --git a/include/hw/hotplug.h b/include/hw/hotplug.h
> > index c0db869..10ca5b6 100644
> > --- a/include/hw/hotplug.h
> > +++ b/include/hw/hotplug.h
> > @@ -47,6 +47,7 @@ typedef void (*hotplug_fn)(HotplugHandler *plug_handler,
> >   * @parent: Opaque parent interface.
> >   * @pre_plug: pre plug callback called at start of device.realize(true)
> >   * @plug: plug callback called at end of device.realize(true).
> > + * @post_pug: post plug callback called after device is successfully plugged.
> this doesn't seem to be necessary,
> why hotplug_handler_plug() isn't sufficient?

At the point of hotplug_handler_plug(), the device is not realize (realized == 
0),
however, nvdimm_get_plugged_device_list() works on realized nvdimm devices.

And we can not move "realized = 1" to the front of hotplug_handler_plug() as 
device
realize routines will check if realized is already been true.