[PATCH v2 0/8] Introduce fwctl subystem

Jason Gunthorpe
2024-06-24T22:47:41Z

fwctl is a new subsystem intended to bring some common rules and order to
the growing pattern of exposing a secure FW interface directly to
userspace. Unlike existing places like RDMA/DRM/VFIO/uacce that are
exposing a device for datapath operations fwctl is focused on debugging,
configuration and provisioning of the device. It will not have the
necessary features like interrupt delivery to support a datapath.

This concept is similar to the long standing practice in the "HW" RAID
space of having a device specific misc device to manager the RAID
controller FW. fwctl generalizes this notion of a companion debug and
management interface that goes along with a dataplane implemented in an
appropriate subsystem.

The need for this has reached a critical point as many users are moving to
run lockdown enabled kernels. Several existing devices have had long
standing tooling for management that relied on /sys/../resource0 or PCI
config space access which is not permitted in lockdown. A major point of
fwctl is to define and document the rules that a device must follow to
expose a lockdown compatible RPC.

Based on some discussion fwctl splits the RPCs into four categories

FWCTL_RPC_CONFIGURATION
FWCTL_RPC_DEBUG_READ_ONLY
FWCTL_RPC_DEBUG_WRITE
FWCTL_RPC_DEBUG_WRITE_FULL

Where the latter two trigger a new TAINT_FWCTL, and the final one requires
CAP_SYS_RAWIO - excluding it from lockdown. The device driver and its FW
would be responsible to restrict RPCs to the requested security scope,
while the core code handles the tainting and CAP checks.

For details see the final patch which introduces the documentation.

This series incorporates a version of the mlx5ctl interface previously
proposed:
https://lore.kernel.org/r/20240207072435.14182-1-saeed@kernel.org/

For this series the memory registration mechanism was removed, but I
expect it will come back.

This series comes with mlx5 as a driver implementation, and I have soft
commitments for at least three more drivers.

There have been two LWN articles written discussing various aspects of
this proposal:

https://lwn.net/Articles/955001/
https://lwn.net/Articles/969383/

Several have expressed general support for this concept:

Broadcom Networking - https://lore.kernel.org/r/Zf2n02q0GevGdS-Z@C02YVCJELVCG
Christoph Hellwig - https://lore.kernel.org/r/Zcx53N8lQjkpEu94@infradead.org/
Enfabrica - https://lore.kernel.org/r/9cc7127f-8674-43bc-b4d7-b1c4c2d96fed@kernel.org/
NVIDIA Networking
Oracle Linux - https://lore.kernel.org/r/6lakj6lxlxhdgrewodvj3xh6sxn3d36t5dab6najzyti2navx3@wrge7cyfk6nq

Work is ongoing for a robust multi-device open source userspace, currently
the mlx5ctl_user that was posted by Saeed has been updated to use fwctl.

https://github.com/saeedtx/mlx5ctl.git
https://github.com/jgunthorpe/mlx5ctl.git

This is on github: https://github.com/jgunthorpe/linux/commits/fwctl

v2:
- Rebase to v6.10-rc5
- Minor style changes
- Follow the style consensus for the guard stuff
- Documentation grammer/spelling
- Add missed length output for mlx5 get_info
- Add two more missed MLX5 CMD's
- Collect tags
v1: https://lore.kernel.org/r/0-v1-9912f1a11620+2a-fwctl_jgg@nvidia.com

Jason Gunthorpe (6):
fwctl: Add basic structure for a class subsystem with a cdev
fwctl: Basic ioctl dispatch for the character device
fwctl: FWCTL_INFO to return basic information about the device
taint: Add TAINT_FWCTL
fwctl: FWCTL_RPC to execute a Remote Procedure Call to device firmware
fwctl: Add documentation

Saeed Mahameed (2):
fwctl/mlx5: Support for communicating with mlx5 fw
mlx5: Create an auxiliary device for fwctl_mlx5

Documentation/admin-guide/tainted-kernels.rst | 5 +
Documentation/userspace-api/fwctl.rst | 269 ++++++++++++
Documentation/userspace-api/index.rst | 1 +
.../userspace-api/ioctl/ioctl-number.rst | 1 +
MAINTAINERS | 16 +
drivers/Kconfig | 2 +
drivers/Makefile | 1 +
drivers/fwctl/Kconfig | 23 +
drivers/fwctl/Makefile | 5 +
drivers/fwctl/main.c | 412 ++++++++++++++++++
drivers/fwctl/mlx5/Makefile | 4 +
drivers/fwctl/mlx5/main.c | 337 ++++++++++++++
drivers/net/ethernet/mellanox/mlx5/core/dev.c | 8 +
include/linux/fwctl.h | 112 +++++
include/linux/panic.h | 3 +-
include/uapi/fwctl/fwctl.h | 137 ++++++
include/uapi/fwctl/mlx5.h | 36 ++
kernel/panic.c | 1 +
18 files changed, 1372 insertions(+), 1 deletion(-)
create mode 100644 Documentation/userspace-api/fwctl.rst
create mode 100644 drivers/fwctl/Kconfig
create mode 100644 drivers/fwctl/Makefile
create mode 100644 drivers/fwctl/main.c
create mode 100644 drivers/fwctl/mlx5/Makefile
create mode 100644 drivers/fwctl/mlx5/main.c
create mode 100644 include/linux/fwctl.h
create mode 100644 include/uapi/fwctl/fwctl.h
create mode 100644 include/uapi/fwctl/mlx5.h

base-commit: f2661062f16b2de5d7b6a5c42a9a5c96326b8454
--
2.45.2