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/[email protected] 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)
