[RFC PATCH 0/5] hw/block/nvme: support multi-path for ctrl/ns

[Minwoo Im <minwoo.im.dev@gmail.com>]

Hello,

This series added support for multi-path I/O with multi-controllers and
namespace sharing.  By supporting these features, we can test Linux
kernel mpath(multi-path) code with this NVMe device.

Patches from the first to third added multi-controller support in a NVM
subsystem by adding a mpath.ctrl parameter to nvme device.  The rest of
the patches added namespace sharing support in a NVM subsystem with two
or more controllers by adding mpath.ns parameter to nvme-ns device.

Multi-path enabled in kernel with this series for two controllers with a
namespace:

  root@vm:~/work# nvme list -v
  NVM Express Subsystems

  Subsystem        Subsystem-NQN                                                                                    Controllers
  ---------------- ------------------------------------------------------------------------------------------------ ----------------
  nvme-subsys0     nqn.2019-08.org.qemu:serial                                                                      nvme0, nvme1

  NVM Express Controllers

  Device   SN                   MN                                       FR       TxPort Address        Subsystem    Namespaces
  -------- -------------------- ---------------------------------------- -------- ------ -------------- ------------ ----------------
  nvme0    serial               QEMU NVMe Ctrl                           1.0      pcie   0000:01:00.0   nvme-subsys0 nvme0n1
  nvme1    serial               QEMU NVMe Ctrl                           1.0      pcie   0000:02:00.0   nvme-subsys0 nvme0n1

  NVM Express Namespaces

  Device       NSID     Usage                      Format           Controllers
  ------------ -------- -------------------------- ---------------- ----------------
  nvme0n1      1        268.44  MB / 268.44  MB    512   B +  0 B   nvme0, nvme1

The reason why I put 'RFC' tag to this series is mostly about the last
patch "hw/block/nvme: add namespace sharing param for mpath".  It seems
like QEMU block backing device does not support to be shared among two
or more -device(s).  It means that we just can't give same drive=
property to multiple nvme-ns devices.  This patch has just let -device
maps to -drive one-to-one(1:1), but if namespae sharing is detected and
setup by the host kernel, then a single block device will be selected
for the NVM subsystem.  I'm not sure this is a good start for this
feature, so I put the RFC tag here.

Please kindly review!

Thanks,

Minwoo Im (5):
  hw/block/nvme: add controller id parameter
  nvme: add CMIC enum value for Identify Controller
  hw/block/nvme: add multi-controller param for mpath
  nvme: add NMIC enum value for Identify Namespace
  hw/block/nvme: add namespace sharing param for mpath

 hw/block/nvme-ns.c   | 14 ++++++++++++--
 hw/block/nvme-ns.h   |  2 ++
 hw/block/nvme.c      | 26 ++++++++++++++++++++++++++
 hw/block/nvme.h      |  2 ++
 include/block/nvme.h |  8 ++++++++
 5 files changed, 50 insertions(+), 2 deletions(-)

-- 
2.17.1