Using 3.18 with a device with NVMe, I notice there is no per-partition statistics:

iostat -p ALL
NVME:
...
Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
...
nvme0n1          11.91       187.01        79.49     390648     166056
nvme0n1p1         0.00         0.00         0.00          0          0
nvme0n1p2         0.00         0.00         0.00          0          0
nvme0n1p3         0.00         0.00         0.00          0          0
nvme0n1p4         0.00         0.00         0.00          0          0
nvme0n1p5         0.00         0.00         0.00          0          0
nvme0n1p6         0.00         0.00         0.00          0          0
nvme0n1p7         0.00         0.00         0.00          0          0
nvme0n1p8         0.00         0.00         0.00          0          0
nvme0n1p9         0.00         0.00         0.00          0          0
nvme0n1p10        0.00         0.00         0.00          0          0
nvme0n1p11        0.00         0.00         0.00          0          0
nvme0n1p12        0.00         0.00         0.00          0          0

eMMC:
mmcblk0           1.55        37.50        81.88      78340     171036
mmcblk0p1         0.33         7.41        81.87      15485     171032
mmcblk0p2         0.14         2.45         0.00       5112          0
mmcblk0p3         0.13         6.92         0.00      14448          0
mmcblk0p4         0.14         2.45         0.00       5112          0
mmcblk0p5         0.13         6.92         0.00      14448          0
mmcblk0p6         0.00         0.00         0.00          5          0
mmcblk0p7         0.00         0.00         0.00          1          0
mmcblk0p8         0.12         2.03         0.00       4249          4
mmcblk0p9         0.00         0.00         0.00          1          0
mmcblk0p10        0.00         0.00         0.00          2          0
mmcblk0p11        0.18         3.59         0.00       7496          0
mmcblk0p12        0.11         1.90         0.00       3976          0
mmcblk0rpmb       0.05         0.19         0.00        400          0
mmcblk0boot1      0.46         1.84         0.00       3840          0
mmcblk0boot0      0.46         1.84         0.00       3840          0


The per device counters are correct, just per partition /stat counters are missing.

The issue has been reported on stack overflow:
http://serverfault.com/questions/784639/no-partition-statistics-with-iostat-on-nvme-devices-with-linux