[PATCH v7 00/18] NVMe PCI endpoint target driver

Damien Le Moal
2024-12-20T09:50:48Z

This patch series implements an NVMe target driver for the PCI transport
using the PCI endpoint framework.

The first 5 patches of this series move and cleanup some nvme code that
will be reused in following patches.

Patch 6 introduces the PCI transport type to allow setting up ports for
the new PCI target controller driver. Patch 7 to 10 are improvements of
the target core code to allow creating the PCI controller and processing
its nvme commands without the need to rely on fabrics commands like the
connect command to create the admin and I/O queues.

Patch 11 relaxes the SGL check in nvmet_req_init() to allow for PCI
admin commands (which must use PRPs).

Patches 12 to 16 improve the set/get feature support of the target code
to get closer to achieving NVMe specification compliance. These patches
though do not implement support for some mandatory features.

Patch 17 is the main patch which introduces the NVMe PCI endpoint target
driver. This patch commit message provides and overview of the driver
design and operation.

Finally, patch 18 documents the NVMe PCI endpoint target driver and
provides a user guide explaning how to setup an NVMe PCI endpoint
device.

The patches are base on Linus 6.13-rc3 tree.

This driver has been extensively tested using a Radxa Rock5B board
(RK3588 Arm SoC). Some tests have also been done using a Pine Rockpro64
board. However, this board does not support DMA channels for the PCI
endpoint controller, leading to very poor performance.

Using the Radxa Rock5b board and setting up a 4 queue-pairs controller
with a null-blk block device loop target, performance was measured using
fio as follows:

+----------------------------------+------------------------+
| Workload | IOPS (BW) |
+----------------------------------+------------------------+
| Rand read, 4KB, QD=1, 1 job | 14.3k IOPS |
| Rand read, 4KB, QD=32, 1 job | 80.8k IOPS |
| Rand read, 4KB, QD=32, 4 jobs | 131k IOPS |
| Rand read, 128KB, QD=32, 1 job | 16.7k IOPS (2.18 GB/s) |
| Rand read, 128KB, QD=32, 4 jobs | 17.4k IOPS (2.27 GB/s) |
| Rand read, 512KB, QD=32, 1 job | 5380 IOPS (2.82 GB/s) |
| Rand read, 512KB, QD=32, 4 jobs | 5206 IOPS (2.27 GB/s) |
| Rand write, 128KB, QD=32, 1 job | 9617 IOPS (1.26 GB/s) |
| Rand write, 128KB, QD=32, 4 jobs | 8405 IOPS (1.10 GB/s) |
+----------------------------------+------------------------+

These results use the default MDTS of the NVMe enpoint driver of 512 KB.

This driver is not intended for production use but rather to be a
playground for learning NVMe and exploring/testing new NVMe features
while providing reasonably good performance.

Changes from v6:
- Fixed incorrect bar cleanup in patch 17 causing a NULL pointer
dereference when PERST# is asserted
- Added Mani's review tag to path 18

Changes from v5:
- Rebased on 6.13-rc3
- Addressed most of Mani's comment on patch 17:
- Renaming of functions and data structures
- Error messages format
- Removed dma_enable configfs knob and simplified DMA initialization
and cleanup.
- Simplified some error path
- Fixed up handling of icontrollers with a fixed bar 0 size
Of note is that I did not define macros for the bits of the CAP
register as that would be too much for now since we want to do this
correctly in include/linux/nvme.h by defining all of them, and by
using these definitions in the nvme host and target code. This can be
done in a followup patch series once this is applied.
- Fixed the command examples in patch 18

Changes from v4:
- Fixed typos in patch 13 and 17 commit message
- Addressed Bjorn's comments (typos and text clarity) in patch 18.
- Added Bjorn's Acked-by tag to patch 18

Changes from v3:
- Added patch 1 which was missing from v3 and caused the 0day build
failure
- Corrected a few typos in the documentation (patch 18)
- Added Christoph's review tag and Rick's tested tag

Changes from v2:
- Changed all preparatory patches before patch 16 to move more NVMe
generic code out of the PCI endpoint target driver and into the
target core.
- Changed patch 16 to use directly a target controller instead of a
host controller. Many aspects of the command management and DMA
transfer management have also been simplified, leading to higher
performance.
- Change the documentation patch to match the above changes

Changes from v1:
- Added review tag to patch 1
- Modified patch 4 to:
- Add Rick's copyright notice
- Improve admin command handling (set_features command) to handle the
number of queues feature (among others) to enable Windows host
- Improved SQ and CQ work items handling

Damien Le Moal (18):
nvme: Move opcode string helper functions declarations
nvmet: Add vendor_id and subsys_vendor_id subsystem attributes
nvmet: Export nvmet_update_cc() and nvmet_cc_xxx() helpers
nvmet: Introduce nvmet_get_cmd_effects_admin()
nvmet: Add drvdata field to struct nvmet_ctrl
nvme: Add PCI transport type
nvmet: Improve nvmet_alloc_ctrl() interface and implementation
nvmet: Introduce nvmet_req_transfer_len()
nvmet: Introduce nvmet_sq_create() and nvmet_cq_create()
nvmet: Add support for I/O queue management admin commands
nvmet: Do not require SGL for PCI target controller commands
nvmet: Introduce get/set_feature controller operations
nvmet: Implement host identifier set feature support
nvmet: Implement interrupt coalescing feature support
nvmet: Implement interrupt config feature support
nvmet: Implement arbitration feature support
nvmet: New NVMe PCI endpoint function target driver
Documentation: Document the NVMe PCI endpoint target driver

Documentation/PCI/endpoint/index.rst | 1 +
.../PCI/endpoint/pci-nvme-function.rst | 13 +
Documentation/nvme/index.rst | 12 +
.../nvme/nvme-pci-endpoint-target.rst | 368 +++
Documentation/subsystem-apis.rst | 1 +
drivers/nvme/host/nvme.h | 39 -
drivers/nvme/target/Kconfig | 10 +
drivers/nvme/target/Makefile | 2 +
drivers/nvme/target/admin-cmd.c | 388 ++-
drivers/nvme/target/configfs.c | 49 +
drivers/nvme/target/core.c | 266 +-
drivers/nvme/target/discovery.c | 17 +
drivers/nvme/target/fabrics-cmd-auth.c | 14 +-
drivers/nvme/target/fabrics-cmd.c | 101 +-
drivers/nvme/target/nvmet.h | 110 +-
drivers/nvme/target/pci-epf.c | 2610 +++++++++++++++++
include/linux/nvme.h | 42 +
17 files changed, 3883 insertions(+), 160 deletions(-)
create mode 100644 Documentation/PCI/endpoint/pci-nvme-function.rst
create mode 100644 Documentation/nvme/index.rst
create mode 100644 Documentation/nvme/nvme-pci-endpoint-target.rst
create mode 100644 drivers/nvme/target/pci-epf.c

base-commit: 78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8
--
2.47.1