[PATCH v2 0/5] KVM: arm64: fix VGICv3 redistributor rollback

[Karl Mehltretter <kmehltretter@gmail.com>]

A failed REDIST_REGION write can unregister redistributor iodevs while
leaving their cached vCPU assignments and free_index values intact. A retry
then skips those assignments and succeeds with redistributors missing from
the MMIO bus.

Patches 1 and 2 fix VGICv3 redistributor failure handling. Patch 3 cleans
up redistributor teardown. Patches 4 and 5 extend the KVM selftest
infrastructure and add regression coverage.

Patch 1 reserves the current vCPU's region slot before registering its
iodev and releases the assignment if registration fails. This keeps
free_index consistent with the cached assignments.

Patch 2 uses the same cleanup during redistributor unregistration, allowing
the existing rollback to reset the vCPUs processed before the failure.

Patch 3 unregisters redistributors before freeing their regions and removes
the region destructor's now-redundant vCPU scan. It is not required by the
first two patches.

Patch 4 lets the common VGIC setup helper select the guest entry point.

Patch 5 adds a regression test that rejects an overlapping region, retries
at a valid address, and then accesses all four redistributors. It exercises
the failed region update fixed by patch 2. The MMIO bus registration
failure handled by patch 1 is not fault-injected.

Testing: built the patched kernel and selftest in an arm64 Linux Docker
container with GCC 13.3.0. The selftest passed under QEMU 11.0.2 TCG with
-machine virt,virtualization=on,gic-version=3 and -cpu max. The same
selftest against the exact unpatched base failed with:

  Unexpected MMIO exit at 0x8030008

---
Changes since RFC:
- Reset all redistributor assignments after a failed region update.
- Split MMIO bus registration failure, region rollback, and teardown
  cleanup into separate patches.
- Split the selftest infrastructure change from the regression test and
  check all four redistributors after retry.
- Rebase onto the current kvmarm/next.

Previous version:
RFC: https://lore.kernel.org/r/cover.1786344511.git.kmehltretter@gmail.com

Karl Mehltretter (5):
  KVM: arm64: vgic-v3: Undo assignment on iodev registration failure
  KVM: arm64: vgic-v3: Reset assignments after failed region setup
  KVM: arm64: vgic-v3: Unregister redistributors before freeing regions
  KVM: arm64: selftests: Pass guest code to vm_gic_create_with_vcpus()
  KVM: arm64: selftests: Test VGICv3 redistributor region retry

 arch/arm64/kvm/vgic/vgic-init.c               |  11 +-
 arch/arm64/kvm/vgic/vgic-mmio-v3.c            |  33 ++---
 tools/testing/selftests/kvm/arm64/vgic_init.c | 117 ++++++++++++++++--
 3 files changed, 134 insertions(+), 27 deletions(-)


base-commit: 57e7cf13ac26bf1a3dba6cfa601f7b2481811575
-- 
2.39.5 (Apple Git-154)