[PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ

[Wei Wang]

Add a new vq to report hints of guest free pages to the host.

Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
---
 drivers/virtio/virtio_balloon.c     | 164 ++++++++++++++++++++++++++++++------
 include/uapi/linux/virtio_balloon.h |   1 +
 2 files changed, 140 insertions(+), 25 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 29aca0c..29c4a61 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -54,11 +54,12 @@ static struct vfsmount *balloon_mnt;
 
 struct virtio_balloon {
 	struct virtio_device *vdev;
-	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
+	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
 
 	/* The balloon servicing is delegated to a freezable workqueue. */
 	struct work_struct update_balloon_stats_work;
 	struct work_struct update_balloon_size_work;
+	struct work_struct report_free_page_work;
 
 	/* Prevent updating balloon when it is being canceled. */
 	spinlock_t stop_update_lock;
@@ -90,6 +91,13 @@ struct virtio_balloon {
 	/* Memory statistics */
 	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 
+	/*
+	 * Used by the device and driver to signal each other.
+	 * device->driver: start the free page report.
+	 * driver->device: end the free page report.
+	 */
+	__virtio32 report_free_page_signal;
+
 	/* To register callback in oom notifier call chain */
 	struct notifier_block nb;
 };
@@ -146,7 +154,7 @@ static void set_page_pfns(struct virtio_balloon *vb,
 }
 
 static void send_one_sg(struct virtio_balloon *vb, struct virtqueue *vq,
-			void *addr, uint32_t size)
+			void *addr, uint32_t size, bool busywait)
 {
 	struct scatterlist sg;
 	unsigned int len;
@@ -165,7 +173,12 @@ static void send_one_sg(struct virtio_balloon *vb, struct virtqueue *vq,
 			cpu_relax();
 	}
 	virtqueue_kick(vq);
-	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+	if (busywait)
+		while (!virtqueue_get_buf(vq, &len) &&
+		       !virtqueue_is_broken(vq))
+			cpu_relax();
+	else
+		wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 }
 
 /*
@@ -197,11 +210,11 @@ static void tell_host_sgs(struct virtio_balloon *vb,
 		sg_addr = pfn_to_kaddr(sg_pfn_start);
 		sg_len = (sg_pfn_end - sg_pfn_start) << PAGE_SHIFT;
 		while (sg_len > sg_max_len) {
-			send_one_sg(vb, vq, sg_addr, sg_max_len);
+			send_one_sg(vb, vq, sg_addr, sg_max_len, 0);
 			sg_addr += sg_max_len;
 			sg_len -= sg_max_len;
 		}
-		send_one_sg(vb, vq, sg_addr, sg_len);
+		send_one_sg(vb, vq, sg_addr, sg_len, 0);
 		xb_zero(&vb->page_xb, sg_pfn_start, sg_pfn_end);
 		sg_pfn_start = sg_pfn_end + 1;
 	}
@@ -503,42 +516,138 @@ static void update_balloon_size_func(struct work_struct *work)
 		queue_work(system_freezable_wq, work);
 }
 
+static void virtio_balloon_send_free_pages(void *opaque, unsigned long pfn,
+					   unsigned long nr_pages)
+{
+	struct virtio_balloon *vb = (struct virtio_balloon *)opaque;
+	void *addr = pfn_to_kaddr(pfn);
+	uint32_t len = nr_pages << PAGE_SHIFT;
+
+	send_one_sg(vb, vb->free_page_vq, addr, len, 1);
+}
+
+static void report_free_page_completion(struct virtio_balloon *vb)
+{
+	struct virtqueue *vq = vb->free_page_vq;
+	struct scatterlist sg;
+	unsigned int len;
+
+	sg_init_one(&sg, &vb->report_free_page_signal, sizeof(__virtio32));
+	while (unlikely(virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL)
+			== -ENOSPC)) {
+		virtqueue_kick(vq);
+		while (!virtqueue_get_buf(vq, &len) &&
+		       !virtqueue_is_broken(vq))
+			cpu_relax();
+	}
+	virtqueue_kick(vq);
+}
+
+static void report_free_page(struct work_struct *work)
+{
+	struct virtio_balloon *vb;
+
+	vb = container_of(work, struct virtio_balloon, report_free_page_work);
+	walk_free_mem_block(vb, 1, &virtio_balloon_send_free_pages);
+	report_free_page_completion(vb);
+}
+
+static void free_page_request(struct virtqueue *vq)
+{
+	struct virtio_balloon *vb = vq->vdev->priv;
+
+	queue_work(system_freezable_wq, &vb->report_free_page_work);
+}
+
 static int init_vqs(struct virtio_balloon *vb)
 {
-	struct virtqueue *vqs[3];
-	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
-	static const char * const names[] = { "inflate", "deflate", "stats" };
-	int err, nvqs;
+	struct virtqueue **vqs;
+	vq_callback_t **callbacks;
+	const char **names;
+	struct scatterlist sg;
+	int i, nvqs, err = -ENOMEM;
+
+	/* Inflateq and deflateq are used unconditionally */
+	nvqs = 2;
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ))
+		nvqs++;
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ))
+		nvqs++;
+
+	/* Allocate space for find_vqs parameters */
+	vqs = kcalloc(nvqs, sizeof(*vqs), GFP_KERNEL);
+	if (!vqs)
+		goto err_vq;
+	callbacks = kmalloc_array(nvqs, sizeof(*callbacks), GFP_KERNEL);
+	if (!callbacks)
+		goto err_callback;
+	names = kmalloc_array(nvqs, sizeof(*names), GFP_KERNEL);
+	if (!names)
+		goto err_names;
+
+	callbacks[0] = balloon_ack;
+	names[0] = "inflate";
+	callbacks[1] = balloon_ack;
+	names[1] = "deflate";
+
+	i = 2;
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+		callbacks[i] = stats_request;
+		names[i] = "stats";
+		i++;
+	}
 
-	/*
-	 * We expect two virtqueues: inflate and deflate, and
-	 * optionally stat.
-	 */
-	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
-	err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ)) {
+		callbacks[i] = free_page_request;
+		names[i] = "free_page_vq";
+	}
+
+	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names,
+					 NULL, NULL);
 	if (err)
-		return err;
+		goto err_find;
 
 	vb->inflate_vq = vqs[0];
 	vb->deflate_vq = vqs[1];
+	i = 2;
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
-		struct scatterlist sg;
-		unsigned int num_stats;
-		vb->stats_vq = vqs[2];
-
+		vb->stats_vq = vqs[i++];
 		/*
 		 * Prime this virtqueue with one buffer so the hypervisor can
 		 * use it to signal us later (it can't be broken yet!).
 		 */
-		num_stats = update_balloon_stats(vb);
-
-		sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
+		sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 		if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
 		    < 0)
 			BUG();
 		virtqueue_kick(vb->stats_vq);
 	}
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ)) {
+		vb->free_page_vq = vqs[i];
+		vb->report_free_page_signal = 0;
+		sg_init_one(&sg, &vb->report_free_page_signal,
+			    sizeof(__virtio32));
+		if (virtqueue_add_outbuf(vb->free_page_vq, &sg, 1, vb,
+					 GFP_KERNEL) < 0)
+			dev_warn(&vb->vdev->dev, "%s: add signal buf fail\n",
+				 __func__);
+		virtqueue_kick(vb->free_page_vq);
+	}
+
+	kfree(names);
+	kfree(callbacks);
+	kfree(vqs);
 	return 0;
+
+err_find:
+	kfree(names);
+err_names:
+	kfree(callbacks);
+err_callback:
+	kfree(vqs);
+err_vq:
+	return err;
 }
 
 #ifdef CONFIG_BALLOON_COMPACTION
@@ -590,7 +699,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 	if (use_sg) {
 		send_one_sg(vb, vb->inflate_vq, page_address(newpage),
-			    PAGE_SIZE);
+			    PAGE_SIZE, 0);
 	} else {
 		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 		set_page_pfns(vb, vb->pfns, newpage);
@@ -600,7 +709,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 	balloon_page_delete(page);
 	if (use_sg) {
 		send_one_sg(vb, vb->deflate_vq, page_address(page),
-			    PAGE_SIZE);
+			    PAGE_SIZE, 0);
 	} else {
 		vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 		set_page_pfns(vb, vb->pfns, page);
@@ -667,6 +776,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_SG))
 		xb_init(&vb->page_xb);
 
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_VQ))
+		INIT_WORK(&vb->report_free_page_work, report_free_page);
+
 	vb->nb.notifier_call = virtballoon_oom_notify;
 	vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 	err = register_oom_notifier(&vb->nb);
@@ -731,6 +843,7 @@ static void virtballoon_remove(struct virtio_device *vdev)
 	spin_unlock_irq(&vb->stop_update_lock);
 	cancel_work_sync(&vb->update_balloon_size_work);
 	cancel_work_sync(&vb->update_balloon_stats_work);
+	cancel_work_sync(&vb->report_free_page_work);
 
 	xb_empty(&vb->page_xb);
 	remove_common(vb);
@@ -785,6 +898,7 @@ static unsigned int features[] = {
 	VIRTIO_BALLOON_F_STATS_VQ,
 	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 	VIRTIO_BALLOON_F_SG,
+	VIRTIO_BALLOON_F_FREE_PAGE_VQ,
 };
 
 static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 37780a7..8214f84 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -35,6 +35,7 @@
 #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
 #define VIRTIO_BALLOON_F_SG		3 /* Use sg instead of PFN lists */
+#define VIRTIO_BALLOON_F_FREE_PAGE_VQ	4 /* Virtqueue to report free pages */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
-- 
2.7.4