linux-kernel - [PATCH v3 02/10] KVM: arm64: vgic: Use xarray to find LPI in vgic_get

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Date: Fri, 16 Feb 2024 18:41:45 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: kvmarm@...ts.linux.dev
Cc: kvm@...r.kernel.org,
	Marc Zyngier <maz@...nel.org>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-kernel@...r.kernel.org,
	Oliver Upton <oliver.upton@...ux.dev>
Subject: [PATCH v3 02/10] KVM: arm64: vgic: Use xarray to find LPI in vgic_get_lpi()

Iterating over the LPI linked-list is less than ideal when the desired
index is already known. Use the INTID to index the LPI xarray instead.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
 arch/arm64/kvm/vgic/vgic.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index c126014f8395..d90c42ff051d 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -54,8 +54,9 @@ struct vgic_global kvm_vgic_global_state __ro_after_init = {
  */
 
 /*
- * Iterate over the VM's list of mapped LPIs to find the one with a
- * matching interrupt ID and return a reference to the IRQ structure.
+ * Index the VM's xarray of mapped LPIs and return a reference to the IRQ
+ * structure. The caller is expected to call vgic_put_irq() later once it's
+ * finished with the IRQ.
  */
 static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
 {
@@ -65,20 +66,10 @@ static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
 
 	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
 
-	list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
-		if (irq->intid != intid)
-			continue;
-
-		/*
-		 * This increases the refcount, the caller is expected to
-		 * call vgic_put_irq() later once it's finished with the IRQ.
-		 */
+	irq = xa_load(&dist->lpi_xa, intid);
+	if (irq)
 		vgic_get_irq_kref(irq);
-		goto out_unlock;
-	}
-	irq = NULL;
 
-out_unlock:
 	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	return irq;
-- 
2.44.0.rc0.258.g7320e95886-goog