[RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void

[Nicolin Chen <nicolinc@nvidia.com>]

There's only one caller that checks its return value with a WARN_ON_ONCE,
while all other callers do not check return value at all. So simplify the
API to return void by embedding similar WARN_ON_ONCEs.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 .../driver-api/vfio-mediated-device.rst       |  2 +-
 drivers/gpu/drm/i915/gvt/kvmgt.c              |  5 +---
 drivers/vfio/vfio.c                           | 24 ++++++++-----------
 drivers/vfio/vfio.h                           |  2 +-
 drivers/vfio/vfio_iommu_type1.c               | 16 ++++++-------
 include/linux/vfio.h                          |  4 ++--
 6 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index 1c57815619fd..b0fdf76b339a 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -265,7 +265,7 @@ driver::
 	int vfio_pin_pages(struct vfio_device *device, unsigned long *user_pfn,
 				  int npage, int prot, unsigned long *phys_pfn);
 
-	int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
+	void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
 				    int npage);
 
 These functions call back into the back-end IOMMU module by using the pin_pages
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index e2f6c56ab342..8c67c9aba82d 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -231,18 +231,15 @@ static void intel_gvt_cleanup_vgpu_type_groups(struct intel_gvt *gvt)
 static void gvt_unpin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
 		unsigned long size)
 {
-	struct drm_i915_private *i915 = vgpu->gvt->gt->i915;
 	int total_pages;
 	int npage;
-	int ret;
 
 	total_pages = roundup(size, PAGE_SIZE) / PAGE_SIZE;
 
 	for (npage = 0; npage < total_pages; npage++) {
 		unsigned long cur_gfn = gfn + npage;
 
-		ret = vfio_unpin_pages(&vgpu->vfio_device, &cur_gfn, 1);
-		drm_WARN_ON(&i915->drm, ret != 1);
+		vfio_unpin_pages(&vgpu->vfio_device, &cur_gfn, 1);
 	}
 }
 
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 61e71c1154be..01f45ec70a3d 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1959,31 +1959,27 @@ 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_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))
+		return;
 
-	if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
-		return -E2BIG;
+	if (WARN_ON_ONCE(npage > VFIO_PIN_PAGES_MAX_ENTRIES))
+		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;
+	if (WARN_ON_ONCE(unlikely(!driver || !driver->ops->unpin_pages)))
+		return;
+
+	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 a67130221151..bef4edf58138 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);
 	int		(*register_notifier)(void *iommu_data,
 					     unsigned long *events,
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c13b9290e357..08613edaf722 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -948,20 +948,19 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 	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;
+	if (WARN_ON_ONCE(!iommu || !user_pfn || npage <= 0))
+		return;
 
 	/* Supported for v2 version only */
-	if (!iommu->v2)
-		return -EACCES;
+	if (WARN_ON_ONCE(!iommu->v2))
+		return;
 
 	mutex_lock(&iommu->lock);
 
@@ -979,7 +978,8 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
 	}
 
 	mutex_unlock(&iommu->lock);
-	return i > 0 ? i : -EINVAL;
+
+	WARN_ON_ONCE(i != npage);
 }
 
 static long vfio_sync_unpin(struct vfio_dma *dma, struct vfio_domain *domain,
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 49580fa2073a..d0844ecdc961 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -149,8 +149,8 @@ bool vfio_file_has_dev(struct file *file, struct vfio_device *device);
 
 int vfio_pin_pages(struct vfio_device *device, unsigned long *user_pfn,
 		   int npage, int prot, unsigned long *phys_pfn);
-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);
 int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
 		void *data, size_t len, bool write);
 
-- 
2.17.1