vdpa_sim: Implement resume vdpa op

Implement resume operation for vdpa_sim devices, so vhost-vdpa will
offer that backend feature and userspace can effectively resume the
device.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Message-Id: <15a4566826033c5dd9a2167e5cfb0ef4d90cea49.1672742878.git.sebastien.boeuf@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -358,6 +358,12 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 
+	if (!vdpasim->running &&
+	    (vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
+		vdpasim->pending_kick = true;
+		return;
+	}
+
 	if (vq->ready)
 		schedule_work(&vdpasim->work);
 }
@@ -528,6 +534,27 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
 	return 0;
 }
 
+static int vdpasim_resume(struct vdpa_device *vdpa)
+{
+	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+	int i;
+
+	spin_lock(&vdpasim->lock);
+	vdpasim->running = true;
+
+	if (vdpasim->pending_kick) {
+		/* Process pending descriptors */
+		for (i = 0; i < vdpasim->dev_attr.nvqs; ++i)
+			vdpasim_kick_vq(vdpa, i);
+
+		vdpasim->pending_kick = false;
+	}
+
+	spin_unlock(&vdpasim->lock);
+
+	return 0;
+}
+
 static size_t vdpasim_get_config_size(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
@@ -720,6 +747,7 @@ static const struct vdpa_config_ops vdpasim_config_ops = {
 	.set_status             = vdpasim_set_status,
 	.reset			= vdpasim_reset,
 	.suspend		= vdpasim_suspend,
+	.resume			= vdpasim_resume,
 	.get_config_size        = vdpasim_get_config_size,
 	.get_config             = vdpasim_get_config,
 	.set_config             = vdpasim_set_config,
@@ -753,6 +781,7 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops = {
 	.set_status             = vdpasim_set_status,
 	.reset			= vdpasim_reset,
 	.suspend		= vdpasim_suspend,
+	.resume			= vdpasim_resume,
 	.get_config_size        = vdpasim_get_config_size,
 	.get_config             = vdpasim_get_config,
 	.set_config             = vdpasim_set_config,

drivers/vdpa/vdpa_sim/vdpa_sim.h

@@ -67,6 +67,7 @@ struct vdpasim {
 	u64 features;
 	u32 groups;
 	bool running;
+	bool pending_kick;
 	/* spinlock to synchronize iommu table */
 	spinlock_t iommu_lock;
 };