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Subject[RFC PATCH 2/7] iommu: Add share domain interface in iommu for spimdev
Date
From: Kenneth Lee <liguozhu@hisilicon.com>

This patch add sharing interface for a iommu_group. The new interface:

iommu_group_share_domain()
iommu_group_unshare_domain()

can be used by some virtual iommu_group (such as iommu_group for spimdev)
to share their parent's iommu_group.

When the domain of the group is shared, it cannot be changed before
unshared. In the future, notification can be added if update is required.

Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com>
---
drivers/iommu/iommu.c | 28 +++++++++++++++++++++++++++-
include/linux/iommu.h | 2 ++
2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 63b37563db7e..a832aafe660d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -54,6 +54,9 @@ struct iommu_group {
int id;
struct iommu_domain *default_domain;
struct iommu_domain *domain;
+ atomic_t domain_shared_ref; /* Number of user of current domain.
+ * The domain cannot be modified if ref > 0
+ */
};

struct group_device {
@@ -353,6 +356,7 @@ struct iommu_group *iommu_group_alloc(void)
return ERR_PTR(ret);
}
group->id = ret;
+ atomic_set(&group->domain_shared_ref, 0);

ret = kobject_init_and_add(&group->kobj, &iommu_group_ktype,
NULL, "%d", group->id);
@@ -482,6 +486,25 @@ int iommu_group_set_name(struct iommu_group *group, const char *name)
}
EXPORT_SYMBOL_GPL(iommu_group_set_name);

+struct iommu_domain *iommu_group_share_domain(struct iommu_group *group)
+{
+ /* the domain can be shared only when the default domain is used */
+ /* todo: more shareable check */
+ if (group->domain != group->default_domain)
+ return ERR_PTR(-EINVAL);
+
+ atomic_inc(&group->domain_shared_ref);
+ return group->domain;
+}
+EXPORT_SYMBOL_GPL(iommu_group_share_domain);
+
+void iommu_group_unshare_domain(struct iommu_group *group)
+{
+ atomic_dec(&group->domain_shared_ref);
+ WARN_ON(atomic_read(&group->domain_shared_ref) < 0);
+}
+EXPORT_SYMBOL_GPL(iommu_group_unshare_domain);
+
static int iommu_group_create_direct_mappings(struct iommu_group *group,
struct device *dev)
{
@@ -1401,7 +1424,8 @@ static int __iommu_attach_group(struct iommu_domain *domain,
{
int ret;

- if (group->default_domain && group->domain != group->default_domain)
+ if ((group->default_domain && group->domain != group->default_domain) ||
+ atomic_read(&group->domain_shared_ref) > 0)
return -EBUSY;

ret = __iommu_group_for_each_dev(group, domain,
@@ -1438,6 +1462,8 @@ static void __iommu_detach_group(struct iommu_domain *domain,
{
int ret;

+ WARN_ON(atomic_read(&group->domain_shared_ref) > 0);
+
if (!group->default_domain) {
__iommu_group_for_each_dev(group, domain,
iommu_group_do_detach_device);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 19938ee6eb31..278d60e3ec39 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -349,6 +349,8 @@ extern int iommu_domain_get_attr(struct iommu_domain *domain, enum iommu_attr,
void *data);
extern int iommu_domain_set_attr(struct iommu_domain *domain, enum iommu_attr,
void *data);
+extern struct iommu_domain *iommu_group_share_domain(struct iommu_group *group);
+extern void iommu_group_unshare_domain(struct iommu_group *group);

/* Window handling function prototypes */
extern int iommu_domain_window_enable(struct iommu_domain *domain, u32 wnd_nr,
--
2.17.1
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