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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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Sebastian Andrzej Siewior 2018-03-22 16:22:34 +01:00 committed by Joerg Roedel
parent 39ffe39545
commit 779da73273
2 changed files with 11 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
drivers/iommu/amd_iommu.c
View File

@ -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)

2
drivers/iommu/amd_iommu_types.h
View File

@ -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 */