[PATCH v2 2/5] KVM: arm64: vgic-v3: Reset assignments after failed region setup

[Karl Mehltretter <kmehltretter@gmail.com>]

A REDIST_REGION write can fail after redistributors from earlier regions
have been registered. The rollback removes their iodevs from the MMIO bus
but leaves rdreg and base_addr set. It also leaves free_index unchanged. A
retry sees base_addr set and skips registration, leaving the redistributors
absent from the MMIO bus.

Make redistributor unregistration clear the cached assignment and return
the region slot. The failing vCPU already unassigns itself, so the existing
rollback resets the vCPUs processed before the failure. A retry can then
assign and register all redistributors again.

Fixes: c011f4ea106b ("KVM: arm/arm64: Check vcpu redist base before registering an iodev")
Suggested-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 arch/arm64/kvm/vgic/vgic-mmio-v3.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index c75caadbd1d3..331d203acb43 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -852,6 +852,7 @@ void vgic_unregister_redist_iodev(struct kvm_vcpu *vcpu)
 	struct vgic_io_device *rd_dev = &vcpu->arch.vgic_cpu.rd_iodev;
 
 	kvm_io_bus_unregister_dev(vcpu->kvm, KVM_MMIO_BUS, &rd_dev->dev);
+	vgic_unassign_redist_iodev(vcpu);
 }
 
 static int vgic_register_all_redist_iodevs(struct kvm *kvm)
@@ -869,7 +870,7 @@ static int vgic_register_all_redist_iodevs(struct kvm *kvm)
 	}
 
 	if (ret) {
-		/* The current c failed, so iterate over the previous ones. */
+		/* The failing vCPU has no assignment to undo. */
 		int i;
 
 		for (i = 0; i < c; i++) {
-- 
2.39.5 (Apple Git-154)