[PATCH 0/2] KVM: selftests: Link with VFIO selftests lib and test device interrupts

[David Matlack <dmatlack@google.com>]

This series can be found on GitHub:

  https://github.com/dmatlack/linux/tree/kvm/selftests/vfio_pci_irq_test/v1

I'm sending this series out a little early. VFIO selftests has landed in
vfio/next[1] and is slated for 6.18, but has not yet been merged by
Linus. But I wanted to start the discussion of linking the VFIO
selftests library into KVM selftests so we can test VFIO-KVM
interactions.

To demostrate testing VFIO+KVM interactions, patch 2 contains a test to
exercise delivering VFIO device interrupts to vCPUs. This test is
heavily based on Sean's vfio_irq_test.c [2].

Running selftests with VFIO devices is slightly different than typical
KVM selftests since it requires a PCI device bound to vfio-pci. The VFIO
selftests have a helper script for setting up a device:

  $ ./run.sh -s -d 0000:6a:01.0
  + echo "vfio-pci" > /sys/bus/pci/devices/0000:6a:01.0/driver_override
  + echo "0000:6a:01.0" > /sys/bus/pci/drivers/vfio-pci/bind

  Dropping into /bin/bash with VFIO_SELFTESTS_BDF=0000:6a:01.0

The test can then be run and it will detect the $VFIO_SELFTESTS_BDF
environment variable.

  $ tools/testing/selftests/kvm/vfio_pci_irq_test
  $ tools/testing/selftests/kvm/vfio_pci_irq_test -v64 -d -x

You can also pass the BDF directly to the test on the command-line (i.e.
using run.sh and the environment variable is not a required).

  $ tools/testing/selftests/kvm/vfio_pci_irq_test 0000:6a:01.0
  $ tools/testing/selftests/kvm/vfio_pci_irq_test -v64 -d -x 0000:6a:01.0

In order to test with real MSIs generated by the device (-d option), the
device must also have a supported driver in
tools/testing/selftests/vfio/lib/drivers/. At the moment we only have
drivers for Intel CBDMA and Intel DSA devices, so I haven't been able to
test with -d on AMD yet.

Currently this test only supports x86_64, but it should be portable to
at least ARM in the future, so I optimistically placed it in the
top-level KVM selftests directory.

[1] https://github.com/awilliam/linux-vfio/tree/next
[2] https://lore.kernel.org/kvm/20250404193923.1413163-68-seanjc@google.com/

Cc: Sean Christopherson <seanjc@google.com>

David Matlack (2):
  KVM: selftests: Build and link sefltests/vfio/lib into KVM selftests
  KVM: selftests: Add a test for vfio-pci device IRQ delivery to vCPUs

 tools/testing/selftests/kvm/Makefile.kvm      |   6 +-
 .../testing/selftests/kvm/vfio_pci_irq_test.c | 507 ++++++++++++++++++
 2 files changed, 512 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/kvm/vfio_pci_irq_test.c


base-commit: 093458c58f830d0a713fab0de037df5f0ce24fef
prerequisite-patch-id: 72dce9cd586ac36ea378354735d9fabe2f3c445e
prerequisite-patch-id: a8c7ccfd91ce3208f328e8af7b25c83bff8d464d
-- 
2.51.0.384.g4c02a37b29-goog