[PATCH v8 11/29] iommufd/access: Bypass access->ops->unmap for internal use

Nicolin Chen
2025-07-05T01:14:27Z

The access object has been used externally by VFIO mdev devices, allowing
them to pin/unpin physical pages (via needs_pin_pages). Meanwhile, a racy
unmap can occur in this case, so these devices usually implement an unmap
handler, invoked by iommufd_access_notify_unmap().

The new HW queue object will need the same pin/unpin feature, although it
(unlike the mdev case) wants to reject any unmap attempt, during its life
cycle. Instead, it would not implement an unmap handler. Thus, bypass any
access->ops->unmap access call when the access is marked as internal.

Also, an area being pinned by an internal access should reject any unmap
request. This cannot be done inside iommufd_access_notify_unmap() as it's
a per-iopt action. Add a "num_locks" counter in the struct iopt_area, set
that in iopt_area_add_access() when the caller is an internal access.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/iommufd/io_pagetable.h | 5 +++--
drivers/iommu/iommufd/device.c | 18 ++++++++++++------
drivers/iommu/iommufd/io_pagetable.c | 6 ++++++
drivers/iommu/iommufd/pages.c | 12 ++++++++++--
4 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/iommufd/io_pagetable.h b/drivers/iommu/iommufd/io_pagetable.h
index c115a51d9384..b6064f4ce4af 100644
--- a/drivers/iommu/iommufd/io_pagetable.h
+++ b/drivers/iommu/iommufd/io_pagetable.h
@@ -48,6 +48,7 @@ struct iopt_area {
int iommu_prot;
bool prevent_access : 1;
unsigned int num_accesses;
+ unsigned int num_locks;
};

struct iopt_allowed {
@@ -238,9 +239,9 @@ void iopt_pages_unfill_xarray(struct iopt_pages *pages, unsigned long start,

int iopt_area_add_access(struct iopt_area *area, unsigned long start,
unsigned long last, struct page **out_pages,
- unsigned int flags);
+ unsigned int flags, bool lock_area);
void iopt_area_remove_access(struct iopt_area *area, unsigned long start,
- unsigned long last);
+ unsigned long last, bool unlock_area);
int iopt_pages_rw_access(struct iopt_pages *pages, unsigned long start_byte,
void *data, unsigned long length, unsigned int flags);

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 07a4ff753c12..0567faff5680 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -1048,7 +1048,7 @@ static int iommufd_access_change_ioas(struct iommufd_access *access,
}

if (cur_ioas) {
- if (access->ops->unmap) {
+ if (!iommufd_access_is_internal(access) && access->ops->unmap) {
mutex_unlock(&access->ioas_lock);
access->ops->unmap(access->data, 0, ULONG_MAX);
mutex_lock(&access->ioas_lock);
@@ -1255,7 +1255,8 @@ void iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long iova,

xa_lock(&ioas->iopt.access_list);
xa_for_each(&ioas->iopt.access_list, index, access) {
- if (!iommufd_lock_obj(&access->obj))
+ if (!iommufd_lock_obj(&access->obj) ||
+ iommufd_access_is_internal(access))
continue;
xa_unlock(&ioas->iopt.access_list);

@@ -1279,6 +1280,7 @@ void iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long iova,
void iommufd_access_unpin_pages(struct iommufd_access *access,
unsigned long iova, unsigned long length)
{
+ bool internal = iommufd_access_is_internal(access);
struct iopt_area_contig_iter iter;
struct io_pagetable *iopt;
unsigned long last_iova;
@@ -1305,7 +1307,8 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
area, iopt_area_iova_to_index(area, iter.cur_iova),
iopt_area_iova_to_index(
area,
- min(last_iova, iopt_area_last_iova(area))));
+ min(last_iova, iopt_area_last_iova(area))),
+ internal);
WARN_ON(!iopt_area_contig_done(&iter));
up_read(&iopt->iova_rwsem);
mutex_unlock(&access->ioas_lock);
@@ -1354,6 +1357,7 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
unsigned long length, struct page **out_pages,
unsigned int flags)
{
+ bool internal = iommufd_access_is_internal(access);
struct iopt_area_contig_iter iter;
struct io_pagetable *iopt;
unsigned long last_iova;
@@ -1362,7 +1366,8 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,

/* Driver's ops don't support pin_pages */
if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
- WARN_ON(access->iova_alignment != PAGE_SIZE || !access->ops->unmap))
+ WARN_ON(access->iova_alignment != PAGE_SIZE ||
+ (!internal && !access->ops->unmap)))
return -EINVAL;

if (!length)
@@ -1396,7 +1401,7 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
}

rc = iopt_area_add_access(area, index, last_index, out_pages,
- flags);
+ flags, internal);
if (rc)
goto err_remove;
out_pages += last_index - index + 1;
@@ -1419,7 +1424,8 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
iopt_area_iova_to_index(area, iter.cur_iova),
iopt_area_iova_to_index(
area, min(last_iova,
- iopt_area_last_iova(area))));
+ iopt_area_last_iova(area))),
+ internal);
}
up_read(&iopt->iova_rwsem);
mutex_unlock(&access->ioas_lock);
diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
index 22fc3a12109f..abf4aadca96c 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -719,6 +719,12 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, unsigned long start,
goto out_unlock_iova;
}

+ /* The area is locked by an object that has not been destroyed */
+ if (area->num_locks) {
+ rc = -EBUSY;
+ goto out_unlock_iova;
+ }
+
if (area_first < start || area_last > last) {
rc = -ENOENT;
goto out_unlock_iova;
diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c
index cbdde642d2af..301c232462bd 100644
--- a/drivers/iommu/iommufd/pages.c
+++ b/drivers/iommu/iommufd/pages.c
@@ -2111,7 +2111,7 @@ iopt_pages_get_exact_access(struct iopt_pages *pages, unsigned long index,
*/
int iopt_area_add_access(struct iopt_area *area, unsigned long start_index,
unsigned long last_index, struct page **out_pages,
- unsigned int flags)
+ unsigned int flags, bool lock_area)
{
struct iopt_pages *pages = area->pages;
struct iopt_pages_access *access;
@@ -2124,6 +2124,8 @@ int iopt_area_add_access(struct iopt_area *area, unsigned long start_index,
access = iopt_pages_get_exact_access(pages, start_index, last_index);
if (access) {
area->num_accesses++;
+ if (lock_area)
+ area->num_locks++;
access->users++;
iopt_pages_fill_from_xarray(pages, start_index, last_index,
out_pages);
@@ -2145,6 +2147,8 @@ int iopt_area_add_access(struct iopt_area *area, unsigned long start_index,
access->node.last = last_index;
access->users = 1;
area->num_accesses++;
+ if (lock_area)
+ area->num_locks++;
interval_tree_insert(&access->node, &pages->access_itree);
mutex_unlock(&pages->mutex);
return 0;
@@ -2166,7 +2170,7 @@ int iopt_area_add_access(struct iopt_area *area, unsigned long start_index,
* must stop using the PFNs before calling this.
*/
void iopt_area_remove_access(struct iopt_area *area, unsigned long start_index,
- unsigned long last_index)
+ unsigned long last_index, bool unlock_area)
{
struct iopt_pages *pages = area->pages;
struct iopt_pages_access *access;
@@ -2177,6 +2181,10 @@ void iopt_area_remove_access(struct iopt_area *area, unsigned long start_index,
goto out_unlock;

WARN_ON(area->num_accesses == 0 || access->users == 0);
+ if (unlock_area) {
+ WARN_ON(area->num_locks == 0);
+ area->num_locks--;
+ }
area->num_accesses--;
access->users--;
if (access->users)
--
2.43.0