[PATCH v4 0/3] vfio/pci: Support 8-byte PCI loads and stores

[Gerd Bayer <gbayer@linux.ibm.com>]

Hi all,

this all started with a single patch by Ben to enable writing a user-mode
driver for a PCI device that requires 64bit register read/writes on s390.
A quick grep showed that there are several other drivers for PCI devices
in the kernel that use readq/writeq and eventually could use this, too.
So we decided to propose this for general inclusion.

A couple of suggestions for refactorizations by Jason Gunthorpe and Alex
Williamson later [1], I arrived at this little series that avoids some
code duplication in vfio_pci_core_do_io_rw().
Also, I've added a small patch to correct the spelling in one of the
declaration macros that was suggested by Ramesh Thomas [2].

This version was tested with a pass-through PCI device in a KVM guest
and with explicit test reads of size 8, 16, 32, and 64 bit on
s390. For 32bit architectures this has only been compile tested for the
32bit ARM architecture.

Thank you,
Gerd Bayer

[1] https://lore.kernel.org/all/20240422153508.2355844-1-gbayer@linux.ibm.com/
[2] https://lore.kernel.org/kvm/20240425165604.899447-1-gbayer@linux.ibm.com/T/#m1b51fe155c60d04313695fbee11a2ccea856a98c

Changes v3 -> v4:
- Make 64-bit accessors depend on CONFIG_64BIT (for x86, too).
- Drop conversion of if-else if chain to switch-case.
- Add patch to fix spelling of declaration macro.

Changes v2 -> v3:
- Introduce macro to generate body of different-size accesses in
  vfio_pci_core_do_io_rw (courtesy Alex Williamson).
- Convert if-else if chain to a switch-case construct to better
  accommodate conditional compiles.

Changes v1 -> v2:
- On non 64bit architecture use at most 32bit accesses in
  vfio_pci_core_do_io_rw and describe that in the commit message.
- Drop the run-time error on 32bit architectures.
- The #endif splitting the "else if" is not really fortunate, but I'm
  open to suggestions.


Ben Segal (1):
  vfio/pci: Support 8-byte PCI loads and stores

Gerd Bayer (2):
  vfio/pci: Extract duplicated code into macro
  vfio/pci: Fix typo in macro to declare accessors

 drivers/vfio/pci/vfio_pci_rdwr.c | 124 ++++++++++++++++---------------
 include/linux/vfio_pci_core.h    |  27 ++++---
 2 files changed, 78 insertions(+), 73 deletions(-)

-- 
2.45.0