diff mbox series

[v8,16/24] iommufd/device: Add iommufd_access_detach() API

Message ID 20230327094047.47215-17-yi.l.liu@intel.com (mailing list archive)
State New, archived
Headers show
Series Add vfio_device cdev for iommufd support | expand

Commit Message

Yi Liu March 27, 2023, 9:40 a.m. UTC 
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>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/iommu/iommufd/device.c          | 75 +++++++++++++++++++++++--
 drivers/iommu/iommufd/iommufd_private.h |  2 +
 include/linux/iommufd.h                 |  1 +
 3 files changed, 73 insertions(+), 5 deletions(-)

Comments

Jon Pan-Doh March 28, 2023, 2:23 a.m. UTC | #1 
On 2023/3/27 02:40, Yi Liu wrote:
> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> index 2e6e8e217cce..ec2ce3ef187d 100644
> --- a/drivers/iommu/iommufd/iommufd_private.h
> +++ b/drivers/iommu/iommufd/iommufd_private.h
> @@ -263,6 +263,8 @@ 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;

I think you may need to initialize ioas_lock. I got lockdep warnings running
iommufd selftests against this patch. Those went away when I added mutex_init().

---
 drivers/iommu/iommufd/device.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index f0522d80919d..0eaae60f3537 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -474,6 +474,7 @@ 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);
Nicolin Chen March 28, 2023, 3:54 p.m. UTC | #2 
On Mon, Mar 27, 2023 at 07:23:57PM -0700, Jon Pan-Doh wrote:
> External email: Use caution opening links or attachments
> 
> 
> On 2023/3/27 02:40, Yi Liu wrote:
> > diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> > index 2e6e8e217cce..ec2ce3ef187d 100644
> > --- a/drivers/iommu/iommufd/iommufd_private.h
> > +++ b/drivers/iommu/iommufd/iommufd_private.h
> > @@ -263,6 +263,8 @@ 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;
> 
> I think you may need to initialize ioas_lock. I got lockdep warnings running
> iommufd selftests against this patch. Those went away when I added mutex_init().
> 
> ---
>  drivers/iommu/iommufd/device.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index f0522d80919d..0eaae60f3537 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -474,6 +474,7 @@ 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);
> --
> 2.40.0.348.gf938b09366-goog

Yes... I think I lost that when splitting the changes.

Yi, can you help add this in the next version? 

Thanks!
Nicolin
Yi Liu March 29, 2023, 2:24 a.m. UTC | #3 
> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Tuesday, March 28, 2023 11:55 PM
> 
> On Mon, Mar 27, 2023 at 07:23:57PM -0700, Jon Pan-Doh wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On 2023/3/27 02:40, Yi Liu wrote:
> > > diff --git a/drivers/iommu/iommufd/iommufd_private.h
> b/drivers/iommu/iommufd/iommufd_private.h
> > > index 2e6e8e217cce..ec2ce3ef187d 100644
> > > --- a/drivers/iommu/iommufd/iommufd_private.h
> > > +++ b/drivers/iommu/iommufd/iommufd_private.h
> > > @@ -263,6 +263,8 @@ 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;
> >
> > I think you may need to initialize ioas_lock. I got lockdep warnings running
> > iommufd selftests against this patch. Those went away when I added
> mutex_init().
> >
> > ---
> >  drivers/iommu/iommufd/device.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/iommu/iommufd/device.c
> b/drivers/iommu/iommufd/device.c
> > index f0522d80919d..0eaae60f3537 100644
> > --- a/drivers/iommu/iommufd/device.c
> > +++ b/drivers/iommu/iommufd/device.c
> > @@ -474,6 +474,7 @@ 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);
> > --
> > 2.40.0.348.gf938b09366-goog
> 
> Yes... I think I lost that when splitting the changes.
> 
> Yi, can you help add this in the next version?

Sure.
diff mbox series

Patch

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 04a57aa1ae2c..f0522d80919d 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -493,26 +493,66 @@  void iommufd_access_destroy(struct iommufd_access *access)
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_access_destroy, 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 != NULL && access->ioas->obj.id != ioas_id)
+	mutex_lock(&access->ioas_lock);
+	if (access->ioas != NULL && access->ioas->obj.id != ioas_id) {
+		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);
@@ -567,8 +607,8 @@  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;
 
@@ -576,6 +616,13 @@  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(
@@ -585,6 +632,7 @@  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);
 
@@ -630,8 +678,8 @@  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;
@@ -646,6 +694,13 @@  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));
@@ -676,6 +731,7 @@  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:
@@ -690,6 +746,7 @@  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);
@@ -709,8 +766,8 @@  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;
@@ -720,6 +777,13 @@  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));
@@ -746,6 +810,7 @@  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 2e6e8e217cce..ec2ce3ef187d 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -263,6 +263,8 @@  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 ac96df406833..9e0e8894dacc 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -47,6 +47,7 @@  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);
 
 void iommufd_ctx_get(struct iommufd_ctx *ictx);