Commit bf4dc0b2 authored by Wei Wang's avatar Wei Wang Committed by Michael S. Tsirkin
Browse files

virtio-balloon: tweak config_changed implementation 



virtio-ccw has deadlock issues with reading the config space inside the
interrupt context, so we tweak the virtballoon_changed implementation
by moving the config read operations into the related workqueue contexts.
The config_read_bitmap is used as a flag to the workqueue callbacks
about the related config fields that need to be read.

The cmd_id_received is also renamed to cmd_id_received_cache, and
the value should be obtained via virtio_balloon_cmd_id_received.

Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarWei Wang <wei.w.wang@intel.com>
Reviewed-by: default avatarCornelia Huck <cohuck@redhat.com>
Reviewed-by: default avatarHalil Pasic <pasic@linux.ibm.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 86a55978 ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Tested-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent a229989d

drivers/virtio/virtio_balloon.c

+65 −33
Original line number Diff line number Diff line
@@ -61,6 +61,10 @@ enum virtio_balloon_vq { 
	VIRTIO_BALLOON_VQ_MAX

};



enum virtio_balloon_config_read {

	VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,

};



struct virtio_balloon {

	struct virtio_device *vdev;

	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
@@ -77,14 +81,20 @@ struct virtio_balloon { 
	/* Prevent updating balloon when it is being canceled. */

	spinlock_t stop_update_lock;

	bool stop_update;

	/* Bitmap to indicate if reading the related config fields are needed */

	unsigned long config_read_bitmap;



	/* The list of allocated free pages, waiting to be given back to mm */

	struct list_head free_page_list;

	spinlock_t free_page_list_lock;

	/* The number of free page blocks on the above list */

	unsigned long num_free_page_blocks;

	/* The cmd id received from host */

	u32 cmd_id_received;

	/*

	 * The cmd id received from host.

	 * Read it via virtio_balloon_cmd_id_received to get the latest value

	 * sent from host.

	 */

	u32 cmd_id_received_cache;

	/* The cmd id that is actively in use */

	__virtio32 cmd_id_active;

	/* Buffer to store the stop sign */
@@ -390,38 +400,32 @@ static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, 
	return num_returned;

}



static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)

{

	if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))

		return;



	/* No need to queue the work if the bit was already set. */

	if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,

			     &vb->config_read_bitmap))

		return;



	queue_work(vb->balloon_wq, &vb->report_free_page_work);

}



static void virtballoon_changed(struct virtio_device *vdev)

{

	struct virtio_balloon *vb = vdev->priv;

	unsigned long flags;

	s64 diff = towards_target(vb);



	if (diff) {

	spin_lock_irqsave(&vb->stop_update_lock, flags);

		if (!vb->stop_update)

	if (!vb->stop_update) {

		queue_work(system_freezable_wq,

			   &vb->update_balloon_size_work);

		spin_unlock_irqrestore(&vb->stop_update_lock, flags);

	}



	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {

		virtio_cread(vdev, struct virtio_balloon_config,

			     free_page_report_cmd_id, &vb->cmd_id_received);

		if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {

			/* Pass ULONG_MAX to give back all the free pages */

			return_free_pages_to_mm(vb, ULONG_MAX);

		} else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&

			   vb->cmd_id_received !=

			   virtio32_to_cpu(vdev, vb->cmd_id_active)) {

			spin_lock_irqsave(&vb->stop_update_lock, flags);

			if (!vb->stop_update) {

				queue_work(vb->balloon_wq,

					   &vb->report_free_page_work);

		virtio_balloon_queue_free_page_work(vb);

	}

	spin_unlock_irqrestore(&vb->stop_update_lock, flags);

}

	}

}



static void update_balloon_size(struct virtio_balloon *vb)

{
@@ -527,6 +531,17 @@ static int init_vqs(struct virtio_balloon *vb) 
	return 0;

}



static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)

{

	if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,

			       &vb->config_read_bitmap))

		virtio_cread(vb->vdev, struct virtio_balloon_config,

			     free_page_report_cmd_id,

			     &vb->cmd_id_received_cache);



	return vb->cmd_id_received_cache;

}



static int send_cmd_id_start(struct virtio_balloon *vb)

{

	struct scatterlist sg;
@@ -537,7 +552,8 @@ static int send_cmd_id_start(struct virtio_balloon *vb) 
	while (virtqueue_get_buf(vq, &unused))

		;



	vb->cmd_id_active = cpu_to_virtio32(vb->vdev, vb->cmd_id_received);

	vb->cmd_id_active = virtio32_to_cpu(vb->vdev,

					virtio_balloon_cmd_id_received(vb));

	sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));

	err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);

	if (!err)
@@ -620,7 +636,8 @@ static int send_free_pages(struct virtio_balloon *vb) 
		 * stop the reporting.

		 */

		cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);

		if (cmd_id_active != vb->cmd_id_received)

		if (unlikely(cmd_id_active !=

			     virtio_balloon_cmd_id_received(vb)))

			break;



		/*
@@ -637,11 +654,9 @@ static int send_free_pages(struct virtio_balloon *vb) 
	return 0;

}



static void report_free_page_func(struct work_struct *work)

static void virtio_balloon_report_free_page(struct virtio_balloon *vb)

{

	int err;

	struct virtio_balloon *vb = container_of(work, struct virtio_balloon,

						 report_free_page_work);

	struct device *dev = &vb->vdev->dev;



	/* Start by sending the received cmd id to host with an outbuf. */
@@ -659,6 +674,23 @@ static void report_free_page_func(struct work_struct *work) 
		dev_err(dev, "Failed to send a stop id, err = %d\n", err);

}



static void report_free_page_func(struct work_struct *work)

{

	struct virtio_balloon *vb = container_of(work, struct virtio_balloon,

						 report_free_page_work);

	u32 cmd_id_received;



	cmd_id_received = virtio_balloon_cmd_id_received(vb);

	if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {

		/* Pass ULONG_MAX to give back all the free pages */

		return_free_pages_to_mm(vb, ULONG_MAX);

	} else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&

		   cmd_id_received !=

		   virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {

		virtio_balloon_report_free_page(vb);

	}

}



#ifdef CONFIG_BALLOON_COMPACTION

/*

 * virtballoon_migratepage - perform the balloon page migration on behalf of
@@ -885,7 +917,7 @@ static int virtballoon_probe(struct virtio_device *vdev) 
			goto out_del_vqs;

		}

		INIT_WORK(&vb->report_free_page_work, report_free_page_func);

		vb->cmd_id_received = VIRTIO_BALLOON_CMD_ID_STOP;

		vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;

		vb->cmd_id_active = cpu_to_virtio32(vb->vdev,

						  VIRTIO_BALLOON_CMD_ID_STOP);

		vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,

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