KVM: arm/arm64: vgic: Fix source vcpu issues for GICv2 SGI

Now that we make sure we don't inject multiple instances of the
same GICv2 SGI at the same time, we've made another bug more
obvious:

If we exit with an active SGI, we completely lose track of which
vcpu it came from. On the next entry, we restore it with 0 as a
source, and if that wasn't the right one, too bad. While this
doesn't seem to trouble GIC-400, the architectural model gets
offended and doesn't deactivate the interrupt on EOI.

Another connected issue is that we will happilly make pending
an interrupt from another vcpu, overriding the above zero with
something that is just as inconsistent. Don't do that.

The final issue is that we signal a maintenance interrupt when
no pending interrupts are present in the LR. Assuming we've fixed
the two issues above, we end-up in a situation where we keep
exiting as soon as we've reached the active state, and not be
able to inject the following pending.

The fix comes in 3 parts:
- GICv2 SGIs have their source vcpu saved if they are active on
  exit, and restored on entry
- Multi-SGIs cannot go via the Pending+Active state, as this would
  corrupt the source field
- Multi-SGIs are converted to using MI on EOI instead of NPIE

Fixes: 16ca6a607d84bef0 ("KVM: arm/arm64: vgic: Don't populate multiple LRs with the same vintid")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 7 insertions, 23 deletions

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 4b6d72939c42..568c65f852e1 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -719,14 +719,6 @@ static inline void vgic_set_underflow(struct kvm_vcpu *vcpu)
 		vgic_v3_set_underflow(vcpu);
 }
 
-static inline void vgic_set_npie(struct kvm_vcpu *vcpu)
-{
-	if (kvm_vgic_global_state.type == VGIC_V2)
-		vgic_v2_set_npie(vcpu);
-	else
-		vgic_v3_set_npie(vcpu);
-}
-
 /* Requires the ap_list_lock to be held. */
 static int compute_ap_list_depth(struct kvm_vcpu *vcpu,
 				 bool *multi_sgi)
@@ -740,17 +732,15 @@ static int compute_ap_list_depth(struct kvm_vcpu *vcpu,
 	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vgic_cpu->ap_list_lock));
 
 	list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) {
+		int w;
+
 		spin_lock(&irq->irq_lock);
 		/* GICv2 SGIs can count for more than one... */
-		if (vgic_irq_is_sgi(irq->intid) && irq->source) {
-			int w = hweight8(irq->source);
-
-			count += w;
-			*multi_sgi |= (w > 1);
-		} else {
-			count++;
-		}
+		w = vgic_irq_get_lr_count(irq);
 		spin_unlock(&irq->irq_lock);
+
+		count += w;
+		*multi_sgi |= (w > 1);
 	}
 	return count;
 }
@@ -761,7 +751,6 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
 	struct vgic_irq *irq;
 	int count;
-	bool npie = false;
 	bool multi_sgi;
 	u8 prio = 0xff;
 
@@ -791,10 +780,8 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 		if (likely(vgic_target_oracle(irq) == vcpu)) {
 			vgic_populate_lr(vcpu, irq, count++);
 
-			if (irq->source) {
-				npie = true;
+			if (irq->source)
 				prio = irq->priority;
-			}
 		}
 
 		spin_unlock(&irq->irq_lock);
@@ -807,9 +794,6 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 		}
 	}
 
-	if (npie)
-		vgic_set_npie(vcpu);
-
 	vcpu->arch.vgic_cpu.used_lrs = count;
 
 	/* Nuke remaining LRs */