[RFC PATCH v3 0/2] fpga: improve protection against low-level control module unloading

From: Marco Pagani <marpagan@redhat.com>
To: Moritz Fischer <mdf@kernel.org>, Wu Hao <hao.wu@intel.com>,
	Xu Yilun <yilun.xu@intel.com>, Tom Rix <trix@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Marco Pagani <marpagan@redhat.com>,
	linux-kernel@vger.kernel.org, linux-fpga@vger.kernel.org
Subject: [RFC PATCH v3 0/2] fpga: improve protection against low-level control module unloading
Date: Mon, 18 Dec 2023 21:28:07 +0100	[thread overview]
Message-ID: <20231218202809.84253-1-marpagan@redhat.com> (raw)

This RFC proposes a solution to keep protecting the fpga manager against
the unloading of the low-level control modules while addressing the
limitations of the current implementation. Currently, the code assumes
that the low-level module registers a platform driver for the parent
device that is later used by the fpga manager (through the parent
device's driver pointer) to take the low-level module's refcount. This
proposal removes this limitation by adding a module owner field to the
fpga_manager_ops struct. Low-level control modules can statically set
the owner field to THIS_MODULE, and the fpga manager can later use it to
take the low-level module's refcount.

For more context, please refer to these threads:
https://lore.kernel.org/linux-fpga/ZS6hhlvjUcqyv8zL@yilunxu-OptiPlex-7050
https://lore.kernel.org/linux-fpga/ZT9qENE9fE3Z0KCW@yilunxu-OptiPlex-7050

v3:
- Improved locking using Yilun's proposal
v2:
- Fixed protection against races during module removal

Marco Pagani (2):
  fpga: add an owner field and use it to take the low-level module's
    refcount
  fpga: set owner of fpga_manager_ops for existing low-level modules

 drivers/fpga/altera-cvp.c             |  1 +
 drivers/fpga/altera-pr-ip-core.c      |  1 +
 drivers/fpga/altera-ps-spi.c          |  1 +
 drivers/fpga/dfl-fme-mgr.c            |  1 +
 drivers/fpga/fpga-mgr.c               | 50 ++++++++++++++++++---------
 drivers/fpga/ice40-spi.c              |  1 +
 drivers/fpga/lattice-sysconfig.c      |  1 +
 drivers/fpga/machxo2-spi.c            |  1 +
 drivers/fpga/microchip-spi.c          |  1 +
 drivers/fpga/socfpga-a10.c            |  1 +
 drivers/fpga/socfpga.c                |  1 +
 drivers/fpga/stratix10-soc.c          |  1 +
 drivers/fpga/tests/fpga-mgr-test.c    |  1 +
 drivers/fpga/tests/fpga-region-test.c |  1 +
 drivers/fpga/ts73xx-fpga.c            |  1 +
 drivers/fpga/versal-fpga.c            |  1 +
 drivers/fpga/xilinx-spi.c             |  1 +
 drivers/fpga/zynq-fpga.c              |  1 +
 drivers/fpga/zynqmp-fpga.c            |  1 +
 include/linux/fpga/fpga-mgr.h         |  4 +++
 20 files changed, 56 insertions(+), 16 deletions(-)

base-commit: ceb6a6f023fd3e8b07761ed900352ef574010bcb
-- 
2.43.0