[RFC,v3,0/7] Add persistence to NVMe ZNS emulation

Message

Sam Li Jan. 22, 2024, 7 p.m. UTC

ZNS emulation follows NVMe ZNS spec but the state of namespace
zones does not persist accross restarts of QEMU. This patch makes the
metadata of ZNS emulation persistent by using new block layer APIs and
the qcow2 img as backing file. It is the second part after the patches
- adding full zoned storage emulation to qcow2 driver [v7]

The metadata of ZNS emulation divides into two parts, zone metadata and
zone descriptor extension data. The zone metadata is composed of zone
states, zone type, wp and zone attributes. The zone information can be
stored at an uint64_t wp to save space and easy access. The structure of
wp of each zone is as follows:
|0000(4)| zone type (1)| zone attr (8)| wp (51) ||

The zone descriptor extension data is relatively small comparing to the
overall size therefore we adopt the option that store zded of all zones
in an array regardless of the valid bit set.

Creating a zns format qcow2 image file adds one more option zd_extension_size
to zoned device configurations.

For a closer look, you can apply the zns patches on this branch:
https://github.com/sgzerolc/qemu/tree/dev-qcow2-v7
Or use the local zns branch directly:
https://github.com/sgzerolc/qemu/tree/dev-zns-v7

To attach this file as emulated zns drive in the command line of QEMU, use:
  -drive file=${znsimg},id=nvmezns0,format=qcow2,if=none \
  -device nvme-ns,drive=nvmezns0,bus=nvme0,nsid=1,uuid=xxx \

Acked-by: Klaus Jensen <[e-mail]>

---

v2->v3:
- fix compatability issue with the qcow2 patch series [Markus]
- address review comments [Markus]

v1->v2:
- split [v1 2/5] patch to three (doc, config, block layer API)
- adapt qcow2 v6

Sam Li (7):
  docs/qcow2: add zd_extension_size option to the zoned format feature
  qcow2: add zd_extension configurations to zoned metadata
  hw/nvme: use blk_get_*() to access zone info in the block layer
  hw/nvme: add blk_get_zone_extension to access zd_extensions
  hw/nvme: make the metadata of ZNS emulation persistent
  hw/nvme: refactor zone append write using block layer APIs
  hw/nvme: make ZDED persistent

 block/block-backend.c             |   88 ++
 block/qcow2.c                     |  120 ++-
 block/qcow2.h                     |    2 +
 docs/interop/qcow2.txt            |    9 +
 hw/nvme/ctrl.c                    | 1246 ++++++++---------------------
 hw/nvme/ns.c                      |  162 +---
 hw/nvme/nvme.h                    |   95 +--
 include/block/block-common.h      |    9 +
 include/block/block_int-common.h  |    8 +
 include/sysemu/block-backend-io.h |   11 +
 include/sysemu/dma.h              |    3 +
 qapi/block-core.json              |    4 +
 system/dma-helpers.c              |   17 +
 13 files changed, 648 insertions(+), 1126 deletions(-)