Re: [Qemu-devel] [PATCH v3 0/3] pc-dimm: factor out MemoryDevice

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 20 Apr 2018 14:34:53 +0200
David Hildenbrand <david@redhat.com> wrote:

> Right now we can only map PCDIMM/NVDIMM into guest address space. In the
> future, we might want to do the same for virtio devices - e.g.
> virtio-pmem or virtio-mem. Especially, they should be able to live side
> by side to each other.
> 
> E.g. the virto based memory devices regions will not be exposed via ACPI
> and friends. They will be detected just like other virtio devices and
> indicate the applicable memory region. This makes it possible to also use
> them on architectures without memory device detection support (e.g. s390x).
> 
> Let's factor out the memory device code into a MemoryDevice interface.
A couple of high level questions as relevant code is not here:

  1. what would hotplug/unplug call chain look like in case of virtio-pmem device
     (reason I'm asking is that pmem being PCI device would trigger
      PCI bus hotplug controller and then it somehow should piggyback
      to Machine provided hotplug handlers, so I wonder what kind of
      havoc it would cause on hotplug infrastructure)

  2. why not use PCI bar mapping mechanism to do mapping since pmem is PCI device?  

 
> v2 -> v3:
> - "pc-dimm: factor out MemoryDevice interface"
> --> Lookup both classes when comparing (David Gibson)  
> 
> v1 -> v2:
> - Fix compile issues on ppc (still untested  )
> 
> 
> David Hildenbrand (3):
>   pc-dimm: factor out MemoryDevice interface
>   machine: make MemoryHotplugState accessible via the machine
>   pc-dimm: factor out address space logic into MemoryDevice code
> 
>  hw/i386/acpi-build.c                         |   3 +-
>  hw/i386/pc.c                                 |  24 ++-
>  hw/mem/Makefile.objs                         |   1 +
>  hw/mem/memory-device.c                       | 282 +++++++++++++++++++++++++
>  hw/mem/pc-dimm.c                             | 304 +++++++--------------------
>  hw/ppc/spapr.c                               |  24 ++-
>  hw/ppc/spapr_hcall.c                         |   1 +
>  include/hw/boards.h                          |  16 ++
>  include/hw/mem/memory-device.h               |  48 +++++
>  include/hw/mem/pc-dimm.h                     |  26 +--
>  numa.c                                       |   3 +-
>  qmp.c                                        |   4 +-
>  stubs/Makefile.objs                          |   2 +-
>  stubs/{qmp_pc_dimm.c => qmp_memory_device.c} |   4 +-
>  14 files changed, 465 insertions(+), 277 deletions(-)
>  create mode 100644 hw/mem/memory-device.c
>  create mode 100644 include/hw/mem/memory-device.h
>  rename stubs/{qmp_pc_dimm.c => qmp_memory_device.c} (61%)
>