Commit 9a1699bd authored by Cristian Marussi's avatar Cristian Marussi Committed by Sudeep Holla
Browse files

firmware: arm_scmi: Review virtio free_list handling 

Add a new spinlock dedicated to the access of the TX free list and a couple
of helpers to get and put messages back and forth from the free_list.

Link: https://lore.kernel.org/r/20220217131234.50328-3-cristian.marussi@arm.com


Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Skalkin <igor.skalkin@opensynergy.com>
Cc: Peter Hilber <peter.hilber@opensynergy.com>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: default avatarCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent 42e90eb5

drivers/firmware/arm_scmi/virtio.c

+57 −31
Original line number Diff line number Diff line
@@ -40,20 +40,23 @@ 
 *

 * @vqueue: Associated virtqueue

 * @cinfo: SCMI Tx or Rx channel

 * @free_lock: Protects access to the @free_list.

 * @free_list: List of unused scmi_vio_msg, maintained for Tx channels only

 * @is_rx: Whether channel is an Rx channel

 * @max_msg: Maximum number of pending messages for this channel.

 * @lock: Protects access to all members except users.

 * @lock: Protects access to all members except users, free_list.

 * @shutdown_done: A reference to a completion used when freeing this channel.

 * @users: A reference count to currently active users of this channel.

 */

struct scmi_vio_channel {

	struct virtqueue *vqueue;

	struct scmi_chan_info *cinfo;

	/* lock to protect access to the free list. */

	spinlock_t free_lock;

	struct list_head free_list;

	bool is_rx;

	unsigned int max_msg;

	/* lock to protect access to all members except users. */

	/* lock to protect access to all members except users, free_list  */

	spinlock_t lock;

	struct completion *shutdown_done;

	refcount_t users;
@@ -134,18 +137,49 @@ static void scmi_vio_channel_cleanup_sync(struct scmi_vio_channel *vioch) 
	wait_for_completion(vioch->shutdown_done);

}



/* Assumes to be called with vio channel acquired already */

static struct scmi_vio_msg *

scmi_virtio_get_free_msg(struct scmi_vio_channel *vioch)

{

	unsigned long flags;

	struct scmi_vio_msg *msg;



	spin_lock_irqsave(&vioch->free_lock, flags);

	if (list_empty(&vioch->free_list)) {

		spin_unlock_irqrestore(&vioch->free_lock, flags);

		return NULL;

	}



	msg = list_first_entry(&vioch->free_list, typeof(*msg), list);

	list_del_init(&msg->list);

	spin_unlock_irqrestore(&vioch->free_lock, flags);



	return msg;

}



/* Assumes to be called with vio channel acquired already */

static void scmi_virtio_put_free_msg(struct scmi_vio_channel *vioch,

				     struct scmi_vio_msg *msg)

{

	unsigned long flags;



	spin_lock_irqsave(&vioch->free_lock, flags);

	list_add_tail(&msg->list, &vioch->free_list);

	spin_unlock_irqrestore(&vioch->free_lock, flags);

}



static bool scmi_vio_have_vq_rx(struct virtio_device *vdev)

{

	return virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);

}



static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch,

			       struct scmi_vio_msg *msg,

			       struct device *dev)

			       struct scmi_vio_msg *msg)

{

	struct scatterlist sg_in;

	int rc;

	unsigned long flags;

	struct device *dev = &vioch->vqueue->vdev->dev;



	sg_init_one(&sg_in, msg->input, VIRTIO_SCMI_MAX_PDU_SIZE);
@@ -162,17 +196,17 @@ static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch, 
	return rc;

}



/*

 * Assume to be called with channel already acquired or not ready at all;

 * vioch->lock MUST NOT have been already acquired.

 */

static void scmi_finalize_message(struct scmi_vio_channel *vioch,

				  struct scmi_vio_msg *msg)

{

	if (vioch->is_rx) {

		scmi_vio_feed_vq_rx(vioch, msg, vioch->cinfo->dev);

	} else {

		/* Here IRQs are assumed to be already disabled by the caller */

		spin_lock(&vioch->lock);

		list_add(&msg->list, &vioch->free_list);

		spin_unlock(&vioch->lock);

	}

	if (vioch->is_rx)

		scmi_vio_feed_vq_rx(vioch, msg);

	else

		scmi_virtio_put_free_msg(vioch, msg);

}



static void scmi_vio_complete_cb(struct virtqueue *vqueue)
@@ -284,7 +318,6 @@ static bool virtio_chan_available(struct device *dev, int idx) 
static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,

			     bool tx)

{

	unsigned long flags;

	struct scmi_vio_channel *vioch;

	int index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX;

	int i;
@@ -314,13 +347,7 @@ static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, 
		if (!msg->input)

			return -ENOMEM;



		if (tx) {

			spin_lock_irqsave(&vioch->lock, flags);

			list_add_tail(&msg->list, &vioch->free_list);

			spin_unlock_irqrestore(&vioch->lock, flags);

		} else {

			scmi_vio_feed_vq_rx(vioch, msg, cinfo->dev);

		}

		scmi_finalize_message(vioch, msg);

	}



	scmi_vio_channel_ready(vioch, cinfo);
@@ -354,33 +381,31 @@ static int virtio_send_message(struct scmi_chan_info *cinfo, 
	if (!scmi_vio_channel_acquire(vioch))

		return -EINVAL;



	spin_lock_irqsave(&vioch->lock, flags);



	if (list_empty(&vioch->free_list)) {

		spin_unlock_irqrestore(&vioch->lock, flags);

	msg = scmi_virtio_get_free_msg(vioch);

	if (!msg) {

		scmi_vio_channel_release(vioch);

		return -EBUSY;

	}



	msg = list_first_entry(&vioch->free_list, typeof(*msg), list);

	list_del(&msg->list);



	msg_tx_prepare(msg->request, xfer);



	sg_init_one(&sg_out, msg->request, msg_command_size(xfer));

	sg_init_one(&sg_in, msg->input, msg_response_size(xfer));



	spin_lock_irqsave(&vioch->lock, flags);



	rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC);

	if (rc) {

		list_add(&msg->list, &vioch->free_list);

	if (rc)

		dev_err(vioch->cinfo->dev,

			"failed to add to TX virtqueue (%d)\n", rc);

	} else {

	else

		virtqueue_kick(vioch->vqueue);

	}



	spin_unlock_irqrestore(&vioch->lock, flags);



	if (rc)

		scmi_virtio_put_free_msg(vioch, msg);



	scmi_vio_channel_release(vioch);



	return rc;
@@ -457,6 +482,7 @@ static int scmi_vio_probe(struct virtio_device *vdev) 
		unsigned int sz;



		spin_lock_init(&channels[i].lock);

		spin_lock_init(&channels[i].free_lock);

		INIT_LIST_HEAD(&channels[i].free_list);

		channels[i].vqueue = vqs[i];