Commit 779da732 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Joerg Roedel
Browse files

iommu/amd: Turn dev_data_list into a lock less list 



alloc_dev_data() adds new items to dev_data_list and search_dev_data()
is searching for items in this list. Both protect the access to the list
with a spinlock.
There is no need to navigate forth and back within the list and there is
also no deleting of a specific item. This qualifies the list to become a
lock less list and as part of this, the spinlock can be removed.
With this change the ordering of those items within the list is changed:
before the change new items were added to the end of the list, now they
are added to the front. I don't think it matters but wanted to mention
it.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 39ffe395

drivers/iommu/amd_iommu.c

+10 −18
Original line number Diff line number Diff line
@@ -83,8 +83,7 @@ 
static DEFINE_RWLOCK(amd_iommu_devtable_lock);



/* List of all available dev_data structures */

static LIST_HEAD(dev_data_list);

static DEFINE_SPINLOCK(dev_data_list_lock);

static LLIST_HEAD(dev_data_list);



LIST_HEAD(ioapic_map);

LIST_HEAD(hpet_map);
@@ -203,40 +202,33 @@ static struct dma_ops_domain* to_dma_ops_domain(struct protection_domain *domain 
static struct iommu_dev_data *alloc_dev_data(u16 devid)

{

	struct iommu_dev_data *dev_data;

	unsigned long flags;



	dev_data = kzalloc(sizeof(*dev_data), GFP_KERNEL);

	if (!dev_data)

		return NULL;



	dev_data->devid = devid;



	spin_lock_irqsave(&dev_data_list_lock, flags);

	list_add_tail(&dev_data->dev_data_list, &dev_data_list);

	spin_unlock_irqrestore(&dev_data_list_lock, flags);



	ratelimit_default_init(&dev_data->rs);



	llist_add(&dev_data->dev_data_list, &dev_data_list);

	return dev_data;

}



static struct iommu_dev_data *search_dev_data(u16 devid)

{

	struct iommu_dev_data *dev_data;

	unsigned long flags;

	struct llist_node *node;



	spin_lock_irqsave(&dev_data_list_lock, flags);

	list_for_each_entry(dev_data, &dev_data_list, dev_data_list) {

	if (llist_empty(&dev_data_list))

		return NULL;



	node = dev_data_list.first;

	llist_for_each_entry(dev_data, node, dev_data_list) {

		if (dev_data->devid == devid)

			goto out_unlock;

			return dev_data;

	}



	dev_data = NULL;



out_unlock:

	spin_unlock_irqrestore(&dev_data_list_lock, flags);



	return dev_data;

	return NULL;

}



static int __last_alias(struct pci_dev *pdev, u16 alias, void *data)

drivers/iommu/amd_iommu_types.h

+1 −1
Original line number Diff line number Diff line
@@ -627,7 +627,7 @@ struct devid_map { 
 */

struct iommu_dev_data {

	struct list_head list;		  /* For domain->dev_list */

	struct list_head dev_data_list;	  /* For global dev_data_list */

	struct llist_node dev_data_list;  /* For global dev_data_list */

	struct protection_domain *domain; /* Domain the device is bound to */

	u16 devid;			  /* PCI Device ID */

	u16 alias;			  /* Alias Device ID */

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