[PATCH 7/8] KVM: arm/arm64: vgic-its: Check the LPI translation cache on MSI injection

[Marc Zyngier <marc.zyngier@arm.com>]

When performing an MSI injection, let's first check if the translation
is already in the cache. If so, let's inject it quickly without
going through the whole translation process.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 virt/kvm/arm/vgic/vgic-its.c | 58 ++++++++++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic.h     |  1 +
 2 files changed, 59 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index bd76683781e8..3021cbf89b70 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -600,6 +600,42 @@ void vgic_its_invalidate_cache(struct kvm *kvm)
 	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 }
 
+static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db,
+					     u32 devid, u32 eventid)
+{
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	struct vgic_translation_cache_entry *cte;
+	struct vgic_irq *irq = NULL;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
+
+	list_for_each_entry(cte, &dist->lpi_translation_cache, entry) {
+		/*
+		 * If we hit a NULL entry, there is nothing after this
+		 * point.
+		 */
+		if (!cte->irq)
+			break;
+
+		if (cte->db == db &&
+		    cte->devid == devid &&
+		    cte->eventid == eventid) {
+			/*
+			 * Move this entry to the head, as it is the
+			 * most recently used.
+			 */
+			list_move(&cte->entry, &dist->lpi_translation_cache);
+			irq = cte->irq;
+			break;
+		}
+	}
+
+	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
+
+	return irq;
+}
+
 int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
 			 u32 devid, u32 eventid, struct vgic_irq **irq)
 {
@@ -683,6 +719,25 @@ static int vgic_its_trigger_msi(struct kvm *kvm, struct vgic_its *its,
 	return 0;
 }
 
+int vgic_its_inject_cached_translation(struct kvm *kvm, struct kvm_msi *msi)
+{
+	struct vgic_irq *irq;
+	unsigned long flags;
+	phys_addr_t db;
+
+	db = (u64)msi->address_hi << 32 | msi->address_lo;
+	irq = vgic_its_check_cache(kvm, db, msi->devid, msi->data);
+
+	if (!irq)
+		return -1;
+
+	raw_spin_lock_irqsave(&irq->irq_lock, flags);
+	irq->pending_latch = true;
+	vgic_queue_irq_unlock(kvm, irq, flags);
+
+	return 0;
+}
+
 /*
  * Queries the KVM IO bus framework to get the ITS pointer from the given
  * doorbell address.
@@ -694,6 +749,9 @@ int vgic_its_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
 	struct vgic_its *its;
 	int ret;
 
+	if (!vgic_its_inject_cached_translation(kvm, msi))
+		return 1;
+
 	its = vgic_msi_to_its(kvm, msi);
 	if (IS_ERR(its))
 		return PTR_ERR(its);
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 04335e997907..fb2c83d6f748 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -317,6 +317,7 @@ int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr);
 int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
 			 u32 devid, u32 eventid, struct vgic_irq **irq);
 struct vgic_its *vgic_msi_to_its(struct kvm *kvm, struct kvm_msi *msi);
+int vgic_its_inject_cached_translation(struct kvm *kvm, struct kvm_msi *msi);
 void vgic_lpi_translation_cache_init(struct kvm *kvm);
 void vgic_its_invalidate_cache(struct kvm *kvm);
 
-- 
2.20.1

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