linux-kernel - [PATCH v3 09/11] vduse: Signal interrupt's eventfd directly in vhost-vdpa case

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Date:   Tue, 28 Feb 2023 17:41:08 +0800
From:   Xie Yongji <xieyongji@...edance.com>
To:     mst@...hat.com, jasowang@...hat.com, tglx@...utronix.de, hch@....de
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 09/11] vduse: Signal interrupt's eventfd directly in vhost-vdpa case

Now the vdpa callback will associate an eventfd in
vhost-vdpa case. For performance reasons, VDUSE can
signal it directly during irq injection.

Signed-off-by: Xie Yongji <xieyongji@...edance.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 869cc7860d82..56f3c2480c2a 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -461,6 +461,7 @@ static void vduse_dev_reset(struct vduse_dev *dev)
 		spin_lock(&vq->irq_lock);
 		vq->cb.callback = NULL;
 		vq->cb.private = NULL;
+		vq->cb.irq_ctx = NULL;
 		spin_unlock(&vq->irq_lock);
 		flush_work(&vq->inject);
 		flush_work(&vq->kick);
@@ -526,6 +527,7 @@ static void vduse_vdpa_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
 	spin_lock(&vq->irq_lock);
 	vq->cb.callback = cb->callback;
 	vq->cb.private = cb->private;
+	vq->cb.irq_ctx = cb->irq_ctx;
 	spin_unlock(&vq->irq_lock);
 }
 
@@ -1020,6 +1022,20 @@ static void vduse_vq_irq_inject(struct work_struct *work)
 	spin_unlock_irq(&vq->irq_lock);
 }
 
+static bool vduse_vq_signal_irqfd(struct vduse_virtqueue *vq)
+{
+	bool signal = false;
+
+	spin_lock_irq(&vq->irq_lock);
+	if (vq->ready && vq->cb.irq_ctx) {
+		eventfd_signal(vq->cb.irq_ctx, 1);
+		signal = true;
+	}
+	spin_unlock_irq(&vq->irq_lock);
+
+	return signal;
+}
+
 static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
 				    struct work_struct *irq_work,
 				    int irq_effective_cpu)
@@ -1322,11 +1338,14 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 		if (index >= dev->vq_num)
 			break;
 
+		ret = 0;
 		index = array_index_nospec(index, dev->vq_num);
-
-		vduse_vq_update_effective_cpu(dev->vqs[index]);
-		ret = vduse_dev_queue_irq_work(dev, &dev->vqs[index]->inject,
-					dev->vqs[index]->irq_effective_cpu);
+		if (!vduse_vq_signal_irqfd(dev->vqs[index])) {
+			vduse_vq_update_effective_cpu(dev->vqs[index]);
+			ret = vduse_dev_queue_irq_work(dev,
+						&dev->vqs[index]->inject,
+						dev->vqs[index]->irq_effective_cpu);
+		}
 		break;
 	}
 	case VDUSE_IOTLB_REG_UMEM: {
-- 
2.20.1