Merge branch 'kvm-arm64/misc' into kvmarm/next

* kvm-arm64/misc:
  : Miscellaneous fixes/cleanups for KVM/arm64
  :
  :  - Avoid GICv4 vLPI configuration when confronted with user error
  :
  :  - Only attempt vLPI configuration when the target routing is an MSI
  :
  :  - Document ordering requirements to avoid aforementioned user error
  KVM: arm64: Tear down vGIC on failed vCPU creation
  KVM: arm64: Document ordering requirements for irqbypass
  KVM: arm64: vgic-v4: Fall back to software irqbypass if LPI not found
  KVM: arm64: vgic-v4: Only WARN for HW IRQ mismatch when unmapping vLPI
  KVM: arm64: vgic-v4: Only attempt vLPI mapping for actual MSIs

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

3 files changed, 32 insertions, 8 deletions

diff --git a/Documentation/virt/kvm/devices/arm-vgic-its.rst b/Documentation/virt/kvm/devices/arm-vgic-its.rst
index e053124f77c4..0f971f83205a 100644
--- a/Documentation/virt/kvm/devices/arm-vgic-its.rst
+++ b/Documentation/virt/kvm/devices/arm-vgic-its.rst
@@ -126,7 +126,8 @@ KVM_DEV_ARM_VGIC_GRP_ITS_REGS
 ITS Restore Sequence:
 ---------------------
 
-The following ordering must be followed when restoring the GIC and the ITS:
+The following ordering must be followed when restoring the GIC, ITS, and
+KVM_IRQFD assignments:
 
 a) restore all guest memory and create vcpus
 b) restore all redistributors
@@ -139,6 +140,8 @@ d) restore the ITS in the following order:
      3. Load the ITS table data (KVM_DEV_ARM_ITS_RESTORE_TABLES)
      4. Restore GITS_CTLR
 
+e) restore KVM_IRQFD assignments for MSIs
+
 Then vcpus can be started.
 
 ITS Table ABI REV0:
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 0160b4924351..f2a65470349a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -466,7 +466,11 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	if (err)
 		return err;
 
-	return kvm_share_hyp(vcpu, vcpu + 1);
+	err = kvm_share_hyp(vcpu, vcpu + 1);
+	if (err)
+		kvm_vgic_vcpu_destroy(vcpu);
+
+	return err;
 }
 
 void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
@@ -2714,6 +2718,14 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
 {
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
+	struct kvm_kernel_irq_routing_entry *irq_entry = &irqfd->irq_entry;
+
+	/*
+	 * The only thing we have a chance of directly-injecting is LPIs. Maybe
+	 * one day...
+	 */
+	if (irq_entry->type != KVM_IRQ_ROUTING_MSI)
+		return 0;
 
 	return kvm_vgic_v4_set_forwarding(irqfd->kvm, prod->irq,
 					  &irqfd->irq_entry);
@@ -2723,6 +2735,10 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
 {
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
+	struct kvm_kernel_irq_routing_entry *irq_entry = &irqfd->irq_entry;
+
+	if (irq_entry->type != KVM_IRQ_ROUTING_MSI)
+		return;
 
 	kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq,
 				     &irqfd->irq_entry);
diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index eedecbbbcf31..9f51d58b5f8a 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c
@@ -415,7 +415,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
 	struct vgic_irq *irq;
 	struct its_vlpi_map map;
 	unsigned long flags;
-	int ret;
+	int ret = 0;
 
 	if (!vgic_supports_direct_msis(kvm))
 		return 0;
@@ -430,10 +430,15 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
 
 	mutex_lock(&its->its_lock);
 
-	/* Perform the actual DevID/EventID -> LPI translation. */
-	ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
-				   irq_entry->msi.data, &irq);
-	if (ret)
+	/*
+	 * Perform the actual DevID/EventID -> LPI translation.
+	 *
+	 * Silently exit if translation fails as the guest (or userspace!) has
+	 * managed to do something stupid. Emulated LPI injection will still
+	 * work if the guest figures itself out at a later time.
+	 */
+	if (vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
+				 irq_entry->msi.data, &irq))
 		goto out;
 
 	/* Silently exit if the vLPI is already mapped */
@@ -512,7 +517,7 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
 	if (ret)
 		goto out;
 
-	WARN_ON(!(irq->hw && irq->host_irq == virq));
+	WARN_ON(irq->hw && irq->host_irq != virq);
 	if (irq->hw) {
 		atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
 		irq->hw = false;