[PATCH v11 14/23] iommufd/device: Add iommufd_access_detach() API

Yi Liu
2023-05-13T13:29:21Z

From: Nicolin Chen <nicolinc@nvidia.com>

Previously, the detach routine is only done by the destroy(). And it was
called by vfio_iommufd_emulated_unbind() when the device runs close(), so
all the mappings in iopt were cleaned in that setup, when the call trace
reaches this detach() routine.

Now, there's a need of a detach uAPI, meaning that it does not only need
a new iommufd_access_detach() API, but also requires access->ops->unmap()
call as a cleanup. So add one.

However, leaving that unprotected can introduce some potential of a race
condition during the pin_/unpin_pages() call, where access->ioas->iopt is
getting referenced. So, add an ioas_lock to protect the context of iopt
referencings.

Also, to allow the iommufd_access_unpin_pages() callback to happen via
this unmap() call, add an ioas_unpin pointer, so the unpin routine won't
be affected by the "access->ioas = NULL" trick.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Terrence Xu <terrence.xu@intel.com>
Tested-by: Yanting Jiang <yanting.jiang@intel.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/iommu/iommufd/device.c | 76 +++++++++++++++++++++++--
drivers/iommu/iommufd/iommufd_private.h | 2 +
include/linux/iommufd.h | 1 +
3 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 5e5f7912807b..a4e0f3d2ac37 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -485,6 +485,7 @@ iommufd_access_create(struct iommufd_ctx *ictx,
iommufd_ctx_get(ictx);
iommufd_object_finalize(ictx, &access->obj);
*id = access->obj.id;
+ mutex_init(&access->ioas_lock);
return access;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_create, IOMMUFD);
@@ -516,26 +517,66 @@ u32 iommufd_access_to_id(struct iommufd_access *access)
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_to_id, IOMMUFD);

+static void __iommufd_access_detach(struct iommufd_access *access)
+{
+ struct iommufd_ioas *cur_ioas = access->ioas;
+
+ lockdep_assert_held(&access->ioas_lock);
+ /*
+ * 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) {
+ 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);
+ refcount_dec(&cur_ioas->obj.users);
+}
+
+void iommufd_access_detach(struct iommufd_access *access)
+{
+ mutex_lock(&access->ioas_lock);
+ if (WARN_ON(!access->ioas))
+ goto out;
+ __iommufd_access_detach(access);
+out:
+ access->ioas_unpin = 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;

- if (access->ioas)
+ mutex_lock(&access->ioas_lock);
+ if (access->ioas) {
+ mutex_unlock(&access->ioas_lock);
return -EINVAL;
+ }

new_ioas = iommufd_get_ioas(access->ictx, ioas_id);
- if (IS_ERR(new_ioas))
+ 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;
+ mutex_unlock(&access->ioas_lock);
return 0;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, IOMMUFD);
@@ -590,8 +631,8 @@ 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)
{
- struct io_pagetable *iopt = &access->ioas->iopt;
struct iopt_area_contig_iter iter;
+ struct io_pagetable *iopt;
unsigned long last_iova;
struct iopt_area *area;

@@ -599,6 +640,13 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
WARN_ON(check_add_overflow(iova, length - 1, &last_iova)))
return;

+ mutex_lock(&access->ioas_lock);
+ if (!access->ioas_unpin) {
+ mutex_unlock(&access->ioas_lock);
+ return;
+ }
+ iopt = &access->ioas_unpin->iopt;
+
down_read(&iopt->iova_rwsem);
iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
iopt_area_remove_access(
@@ -608,6 +656,7 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
min(last_iova, iopt_area_last_iova(area))));
up_read(&iopt->iova_rwsem);
WARN_ON(!iopt_area_contig_done(&iter));
+ mutex_unlock(&access->ioas_lock);
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_unpin_pages, IOMMUFD);

@@ -653,8 +702,8 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
unsigned long length, struct page **out_pages,
unsigned int flags)
{
- struct io_pagetable *iopt = &access->ioas->iopt;
struct iopt_area_contig_iter iter;
+ struct io_pagetable *iopt;
unsigned long last_iova;
struct iopt_area *area;
int rc;
@@ -669,6 +718,13 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
if (check_add_overflow(iova, length - 1, &last_iova))
return -EOVERFLOW;

+ mutex_lock(&access->ioas_lock);
+ if (!access->ioas) {
+ mutex_unlock(&access->ioas_lock);
+ return -ENOENT;
+ }
+ iopt = &access->ioas->iopt;
+
down_read(&iopt->iova_rwsem);
iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
unsigned long last = min(last_iova, iopt_area_last_iova(area));
@@ -699,6 +755,7 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
}

up_read(&iopt->iova_rwsem);
+ mutex_unlock(&access->ioas_lock);
return 0;

err_remove:
@@ -713,6 +770,7 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
iopt_area_last_iova(area))));
}
up_read(&iopt->iova_rwsem);
+ mutex_unlock(&access->ioas_lock);
return rc;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_pin_pages, IOMMUFD);
@@ -732,8 +790,8 @@ EXPORT_SYMBOL_NS_GPL(iommufd_access_pin_pages, IOMMUFD);
int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
void *data, size_t length, unsigned int flags)
{
- struct io_pagetable *iopt = &access->ioas->iopt;
struct iopt_area_contig_iter iter;
+ struct io_pagetable *iopt;
struct iopt_area *area;
unsigned long last_iova;
int rc;
@@ -743,6 +801,13 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
if (check_add_overflow(iova, length - 1, &last_iova))
return -EOVERFLOW;

+ mutex_lock(&access->ioas_lock);
+ if (!access->ioas) {
+ mutex_unlock(&access->ioas_lock);
+ return -ENOENT;
+ }
+ iopt = &access->ioas->iopt;
+
down_read(&iopt->iova_rwsem);
iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
unsigned long last = min(last_iova, iopt_area_last_iova(area));
@@ -769,6 +834,7 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
rc = -ENOENT;
err_out:
up_read(&iopt->iova_rwsem);
+ mutex_unlock(&access->ioas_lock);
return rc;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_rw, IOMMUFD);
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index b38e67d1988b..3dcaf86aab97 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -285,6 +285,8 @@ struct iommufd_access {
struct iommufd_object obj;
struct iommufd_ctx *ictx;
struct iommufd_ioas *ioas;
+ struct iommufd_ioas *ioas_unpin;
+ struct mutex ioas_lock;
const struct iommufd_access_ops *ops;
void *data;
unsigned long iova_alignment;
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index e49c16cd6831..d953d3305d62 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -48,6 +48,7 @@ iommufd_access_create(struct iommufd_ctx *ictx,
const struct iommufd_access_ops *ops, void *data, u32 *id);
void iommufd_access_destroy(struct iommufd_access *access);
int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id);
+void iommufd_access_detach(struct iommufd_access *access);

struct iommufd_ctx *iommufd_access_to_ictx(struct iommufd_access *access);
u32 iommufd_access_to_id(struct iommufd_access *access);
--
2.34.1