[PATCH 0/8] selftests/vfio: igb: 82576 hardware compatibility

[Alex Williamson <alex.williamson@nvidia.com>]

This series is based on Josh Hilke's initial igb selftest driver
posted as:

  https://lore.kernel.org/all/20260511211839.2781731-1-jrhilke@google.com/

That posting validated the driver against QEMU's emulated igb only; it
has not been tested on physical 82576 hardware.  Real 82576 silicon
rejects several of the shortcuts the submitted driver relies on (MAC
loopback, legacy TX descriptors, read-to-clear EICR, autoneg-based
link bring-up, and an unbounded fault-recovery story), and adding
real-hardware coverage is the goal here.

Two of the patches add accommodations specifically for QEMU's emulated
igb (which does not implement PHY-register-0 bit 14 and does not drive
STATUS.LU from CTRL.SLU) so that Josh's "run selftests without
hardware" workflow continues to work.  One of these (RCTL.LBM_MAC)
deviates from datasheet 8.10.1 guidance; empirically the bit has no
observable effect on real 82576 because MAC loopback is not
implemented (3.5.6.2).  See patch 1 for both rationales.

  1) selftests/vfio: igb: Use PHY internal loopback on 82576

     Replace MAC-loopback-via-RCTL.LBM_MAC and PHY autonegotiation with
     PHY internal loopback per datasheet 3.5.6.3.1.  Force the MAC link
     state via CTRL.FRCSPD/FRCDPX/SLU since the descriptor engine
     otherwise waits for a real negotiated link.  Keep RCTL.LBM_MAC
     (deviates from 8.10.1 guidance but empirically inert on real
     hardware per 3.5.6.2) and prefix the loopback setup with a
     one-shot autoneg-restart PHY write (the next PHY write clears
     autoneg-enable before autoneg can start, so this is a no-op on
     real silicon); both are required by QEMU's emulation.  Drop the
     dead igb_read_phy() and its now-unused macros.

  2) selftests/vfio: igb: Use advanced TX and RX descriptors

     Program SRRCTL.DESCTYPE for advanced one-buffer receive
     descriptors (datasheet 7.1.5.2, 8.10.2) and build advanced TX data
     descriptors with DEXT/DTYP/IFCS/EOP/PAYLEN (7.2.2.3) rather than
     the simplified legacy format the submitted driver used.  Drop the
     unused legacy TX descriptor macros.

  3) selftests/vfio: igb: Program MSI-X interrupt routing

     Configure GPIE.Multiple_MSIX and GPIE.EIAME (Table 7-47), EIAC
     and EIAM for vector 0 (8.8.5, 8.8.6), and switch EICR clearing
     from read-to-clear to write-to-clear (7.3.4.2 / 8.8.5 forbid
     reading EICR while EIAC is programmed).

  4) selftests/vfio: igb: Extend memcpy completion timeout for line-rate
     hardware

     The submitted 1 ms cap is well below the 32 ms line-rate floor for
     a 4 MB transfer at 1 Gb/s.  Bump to ~200 ms (6x margin).

  5) selftests/vfio: igb: Disable PCIe completion timeout retries

     Clear GCR.Completion_Timeout_Resend (datasheet 8.6.1) so the
     intentional unmapped-IOVA tests do not generate an unbounded
     stream of retried reads on real hardware.

  6) selftests/vfio: Add vfio_pci_irq_reenable() helper

     New libvfio helper that re-issues VFIO_DEVICE_SET_IRQS against
     existing eventfds, for drivers that recover from
     VFIO_DEVICE_RESET without disturbing user-side eventfds (and any
     fd a test fixture may have cached).

  7) selftests/vfio: igb: Factor hardware programming into igb_hw_init()

     Pure refactor splitting igb_init() into a one-shot outer
     (region-size check, BAR map, CTRL.RST, IMC, vfio_pci_msix_enable)
     and a reusable inner that programs the registers CTRL.RST clears.

  8) selftests/vfio: igb: Recover after DMA-read faults

     Add igb_error_reset_and_reinit() and call it from
     igb_memcpy_wait() on completion timeout.  Datasheet 4.2.1.6.1
     describes CTRL.RST as the recovery mechanism, but empirically
     CTRL.RST alone leaves the descriptor engine wedged after a
     DMA-read fault; the 82576 advertises PCIe FLR (datasheet
     4.2.1.5.1) and VFIO_DEVICE_RESET drives it.

Testing:

  - Selftest builds clean at every commit (verified bisect-buildable).
  - QEMU emulated igb via vng on a host kernel built with VFIO and
    Intel IOMMU enabled: vfio_pci_driver_test 35/35 pass across all
    four IOMMU mode permutations.
  - Physical 82576 on Intel Alderlake platform: vfio_pci_driver_test
    35/35 pass across all four IOMMU mode permutations.

Assisted:

  - Series developed primarily with Claude Opus 4.7 with additional
    assistance from GPT 5.5.  Spec references spot checked and cross
    checked against multiple models.

Alex Williamson (8):
  selftests/vfio: igb: Use PHY internal loopback on 82576
  selftests/vfio: igb: Use advanced TX and RX descriptors
  selftests/vfio: igb: Program MSI-X interrupt routing
  selftests/vfio: igb: Extend memcpy completion timeout for line-rate hardware
  selftests/vfio: igb: Disable PCIe completion timeout retries
  selftests/vfio: Add vfio_pci_irq_reenable() helper
  selftests/vfio: igb: Factor hardware programming into igb_hw_init()
  selftests/vfio: igb: Recover after DMA-read faults

 .../selftests/vfio/lib/drivers/igb/igb.c      | 318 +++++++++++++-----
 .../vfio/lib/drivers/igb/registers.h          |  58 +++-
 .../lib/include/libvfio/vfio_pci_device.h     |   2 +
 .../selftests/vfio/lib/vfio_pci_device.c      |  22 ++
 4 files changed, 302 insertions(+), 98 deletions(-)

-- 
2.51.0