vfio: Make vfio_unpin_pages() return void

There's only one caller that checks its return value with a WARN_ON_ONCE,
while all other callers don't check the return value at all. Above that,
an undo function should not fail. So, simplify the API to return void by
embedding similar WARN_ONs.

Also for users to pinpoint which condition fails, separate WARN_ON lines,
yet remove the "driver->ops->unpin_pages" check, since it's unreasonable
for callers to unpin on something totally random that wasn't even pinned.
And remove NULL pointer checks for they would trigger oops vs. warnings.
Note that npage is already validated in the vfio core, thus drop the same
check in the type1 code.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Tested-by: Terrence Xu <terrence.xu@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/20220723020256.30081-2-nicolinc@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

3 files changed, 14 insertions, 24 deletions

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index b3ce8073cfb1..92b10aafae28 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1983,31 +1983,24 @@ EXPORT_SYMBOL(vfio_pin_pages);
  *		   PFNs should not be greater than VFIO_PIN_PAGES_MAX_ENTRIES.
  * @npage [in]   : count of elements in user_pfn array.  This count should not
  *                 be greater than VFIO_PIN_PAGES_MAX_ENTRIES.
- * Return error or number of pages unpinned.
  */
-int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
-		     int npage)
+void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
+		      int npage)
 {
 	struct vfio_container *container;
 	struct vfio_iommu_driver *driver;
-	int ret;
 
-	if (!user_pfn || !npage || !vfio_assert_device_open(device))
-		return -EINVAL;
+	if (WARN_ON(npage <= 0 || npage > VFIO_PIN_PAGES_MAX_ENTRIES))
+		return;
 
-	if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
-		return -E2BIG;
+	if (WARN_ON(!vfio_assert_device_open(device)))
+		return;
 
 	/* group->container cannot change while a vfio device is open */
 	container = device->group->container;
 	driver = container->iommu_driver;
-	if (likely(driver && driver->ops->unpin_pages))
-		ret = driver->ops->unpin_pages(container->iommu_data, user_pfn,
-					       npage);
-	else
-		ret = -ENOTTY;
 
-	return ret;
+	driver->ops->unpin_pages(container->iommu_data, user_pfn, npage);
 }
 EXPORT_SYMBOL(vfio_unpin_pages);
 
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index 4a7db1f3c33e..6a8424b407c7 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -53,7 +53,7 @@ struct vfio_iommu_driver_ops {
 				     unsigned long *user_pfn,
 				     int npage, int prot,
 				     unsigned long *phys_pfn);
-	int		(*unpin_pages)(void *iommu_data,
+	void		(*unpin_pages)(void *iommu_data,
 				       unsigned long *user_pfn, int npage);
 	void		(*register_device)(void *iommu_data,
 					   struct vfio_device *vdev);
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 026a1d2553a2..e49fbe9968ef 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -949,20 +949,16 @@ pin_done:
 	return ret;
 }
 
-static int vfio_iommu_type1_unpin_pages(void *iommu_data,
-					unsigned long *user_pfn,
-					int npage)
+static void vfio_iommu_type1_unpin_pages(void *iommu_data,
+					 unsigned long *user_pfn, int npage)
 {
 	struct vfio_iommu *iommu = iommu_data;
 	bool do_accounting;
 	int i;
 
-	if (!iommu || !user_pfn || npage <= 0)
-		return -EINVAL;
-
 	/* Supported for v2 version only */
-	if (!iommu->v2)
-		return -EACCES;
+	if (WARN_ON(!iommu->v2))
+		return;
 
 	mutex_lock(&iommu->lock);
 
@@ -980,7 +976,8 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
 	}
 
 	mutex_unlock(&iommu->lock);
-	return i > 0 ? i : -EINVAL;
+
+	WARN_ON(i != npage);
 }
 
 static long vfio_sync_unpin(struct vfio_dma *dma, struct vfio_domain *domain,