[PATCH v2 3/7] KVM: arm64: vgic: Allow last_lr_irq to be NULL when LRs are not overflowing

[Marc Zyngier <maz@kernel.org>]

last_lr_irq is always populated when there is any interrupt populated in
the AP list. Not only this is not necessary (it is only useful when we
completely fill the LRs), but this is in the way of further fixes.

Make sure last_lr_irq is kept to NULL when we LRs are not completely
full.

Fixes: 6da5e537f5afe ("KVM: arm64: vgic: Pick EOIcount deactivations from AP-list tail")
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
---
 arch/arm64/kvm/vgic/vgic-v2.c | 6 ++++--
 arch/arm64/kvm/vgic/vgic-v3.c | 6 ++++--
 arch/arm64/kvm/vgic/vgic.c    | 8 +++-----
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
index 7182f63fc9382..70cc53ba810ad 100644
--- a/arch/arm64/kvm/vgic/vgic-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-v2.c
@@ -122,6 +122,10 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 	for (int lr = 0; lr < vgic_cpu->vgic_v2.used_lrs; lr++)
 		vgic_v2_fold_lr(vcpu, cpuif->vgic_lr[lr]);
 
+	cpuif->used_lrs = 0;
+	if (!irq)
+		return;
+
 	/* See the GICv3 equivalent for the EOIcount handling rationale */
 	list_for_each_entry_continue(irq, &vgic_cpu->ap_list_head, ap_list) {
 		u32 lr;
@@ -144,8 +148,6 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 		vgic_v2_fold_lr(vcpu, lr);
 		eoicount--;
 	}
-
-	cpuif->used_lrs = 0;
 }
 
 void vgic_v2_deactivate(struct kvm_vcpu *vcpu, u32 val)
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 726e20a1da6e7..346bacb3198f2 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -155,6 +155,10 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 	for (int lr = 0; lr < cpuif->used_lrs; lr++)
 		vgic_v3_fold_lr(vcpu, cpuif->vgic_lr[lr]);
 
+	cpuif->used_lrs = 0;
+	if (!irq)
+		return;
+
 	/*
 	 * EOIMode=0: use EOIcount to emulate deactivation. We are
 	 * guaranteed to deactivate in reverse order of the activation, so
@@ -188,8 +192,6 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 		vgic_v3_fold_lr(vcpu, lr);
 		eoicount--;
 	}
-
-	cpuif->used_lrs = 0;
 }
 
 void vgic_v3_deactivate(struct kvm_vcpu *vcpu, u64 val)
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index b25303d9919fd..425503e0c5825 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -866,9 +866,6 @@ static void vgic_fold_state(struct kvm_vcpu *vcpu)
 		return;
 	}
 
-	if (!*host_data_ptr(last_lr_irq))
-		return;
-
 	if (kvm_vgic_global_state.type == VGIC_V2)
 		vgic_v2_fold_lr_state(vcpu);
 	else
@@ -1021,11 +1018,12 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 		scoped_guard(raw_spinlock,  &irq->irq_lock) {
 			if (likely(vgic_target_oracle(irq) == vcpu)) {
 				vgic_populate_lr(vcpu, irq, count++);
-				*host_data_ptr(last_lr_irq) = irq;
+				if (count == kvm_vgic_global_state.nr_lr)
+					*host_data_ptr(last_lr_irq) = irq;
 			}
 		}
 
-		if (count == kvm_vgic_global_state.nr_lr)
+		if (*host_data_ptr(last_lr_irq))
 			break;
 	}
 
-- 
2.47.3