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iommufd: Add iommufd_access_change_ioas(_id) helpers

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The complication of the mutex and refcount will be amplified after we
introduce the replace support for accesses. So, add a preparatory change
of a constitutive helper iommufd_access_change_ioas() and its wrapper
iommufd_access_change_ioas_id(). They can simply take care of existing
iommufd_access_attach() and iommufd_access_detach(), properly sequencing
the refcount puts so that they are truely at the end of the sequence after
we know the IOAS pointer is not required any more.

Link: https://lore.kernel.org/r/da0c462532193b447329c4eb975a596f47e49b70.1690523699.git.nicolinc@nvidia.com
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Nicolin Chen 2023-07-27 23:33:25 -07:00 committed by Jason Gunthorpe
parent 5d5c85ff62
commit 9227da7816
1 changed files with 71 additions and 38 deletions
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109
drivers/iommu/iommufd/device.c
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@ -684,6 +684,70 @@ void iommufd_device_detach(struct iommufd_device *idev)
}
EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);
/*
* On success, it will refcount_inc() at a valid new_ioas and refcount_dec() at
* a valid cur_ioas (access->ioas). A caller passing in a valid new_ioas should
* call iommufd_put_object() if it does an iommufd_get_object() for a new_ioas.
*/
static int iommufd_access_change_ioas(struct iommufd_access *access,
struct iommufd_ioas *new_ioas)
{
u32 iopt_access_list_id = access->iopt_access_list_id;
struct iommufd_ioas *cur_ioas = access->ioas;
int rc;
lockdep_assert_held(&access->ioas_lock);
/* We are racing with a concurrent detach, bail */
if (cur_ioas != access->ioas_unpin)
return -EBUSY;
if (cur_ioas == new_ioas)
return 0;
/*
* Set ioas to NULL to block any further iommufd_access_pin_pages().
* iommufd_access_unpin_pages() can continue using access->ioas_unpin.
*/
access->ioas = NULL;
if (new_ioas) {
rc = iopt_add_access(&new_ioas->iopt, access);
if (rc) {
access->ioas = cur_ioas;
return rc;
}
refcount_inc(&new_ioas->obj.users);
}
if (cur_ioas) {
if (access->ops->unmap) {
mutex_unlock(&access->ioas_lock);
access->ops->unmap(access->data, 0, ULONG_MAX);
mutex_lock(&access->ioas_lock);
}
iopt_remove_access(&cur_ioas->iopt, access, iopt_access_list_id);
refcount_dec(&cur_ioas->obj.users);
}
access->ioas = new_ioas;
access->ioas_unpin = new_ioas;
return 0;
}
static int iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id)
{
struct iommufd_ioas *ioas = iommufd_get_ioas(access->ictx, id);
int rc;
if (IS_ERR(ioas))
return PTR_ERR(ioas);
rc = iommufd_access_change_ioas(access, ioas);
iommufd_put_object(&ioas->obj);
return rc;
}
void iommufd_access_destroy_object(struct iommufd_object *obj)
{
struct iommufd_access *access =
@ -761,60 +825,29 @@ EXPORT_SYMBOL_NS_GPL(iommufd_access_destroy, IOMMUFD);
void iommufd_access_detach(struct iommufd_access *access)
{
struct iommufd_ioas *cur_ioas = access->ioas;
mutex_lock(&access->ioas_lock);
if (WARN_ON(!access->ioas))
goto out;
/*
* Set ioas to NULL to block any further iommufd_access_pin_pages().
* iommufd_access_unpin_pages() can continue using access->ioas_unpin.
*/
access->ioas = NULL;
if (access->ops->unmap) {
if (WARN_ON(!access->ioas)) {
mutex_unlock(&access->ioas_lock);
access->ops->unmap(access->data, 0, ULONG_MAX);
mutex_lock(&access->ioas_lock);
return;
}
iopt_remove_access(&cur_ioas->iopt, access,
access->iopt_access_list_id);
refcount_dec(&cur_ioas->obj.users);
out:
access->ioas_unpin = NULL;
WARN_ON(iommufd_access_change_ioas(access, NULL));
mutex_unlock(&access->ioas_lock);
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_detach, IOMMUFD);
int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id)
{
struct iommufd_ioas *new_ioas;
int rc = 0;
int rc;
mutex_lock(&access->ioas_lock);
if (WARN_ON(access->ioas || access->ioas_unpin)) {
if (WARN_ON(access->ioas)) {
mutex_unlock(&access->ioas_lock);
return -EINVAL;
}
new_ioas = iommufd_get_ioas(access->ictx, ioas_id);
if (IS_ERR(new_ioas)) {
mutex_unlock(&access->ioas_lock);
return PTR_ERR(new_ioas);
}
rc = iopt_add_access(&new_ioas->iopt, access);
if (rc) {
mutex_unlock(&access->ioas_lock);
iommufd_put_object(&new_ioas->obj);
return rc;
}
iommufd_ref_to_users(&new_ioas->obj);
access->ioas = new_ioas;
access->ioas_unpin = new_ioas;
rc = iommufd_access_change_ioas_id(access, ioas_id);
mutex_unlock(&access->ioas_lock);
return 0;
return rc;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, IOMMUFD);