vfio/platform: Use open_device() instead of open coding a refcnt scheme

Platform simply wants to run some code when the device is first
opened/last closed. Use the core framework and locking for this.  Aside
from removing a bit of code this narrows the locking scope from a global
lock.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/7-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/platform/vfio_platform_common.c

@@ -218,74 +218,59 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev,
 	return -EINVAL;
 }
 
-static void vfio_platform_release(struct vfio_device *core_vdev)
+static void vfio_platform_close_device(struct vfio_device *core_vdev)
 {
 	struct vfio_platform_device *vdev =
 		container_of(core_vdev, struct vfio_platform_device, vdev);
+	const char *extra_dbg = NULL;
+	int ret;
 
-	mutex_lock(&driver_lock);
-
-	if (!(--vdev->refcnt)) {
-		const char *extra_dbg = NULL;
-		int ret;
-
-		ret = vfio_platform_call_reset(vdev, &extra_dbg);
-		if (ret && vdev->reset_required) {
-			dev_warn(vdev->device, "reset driver is required and reset call failed in release (%d) %s\n",
-				 ret, extra_dbg ? extra_dbg : "");
-			WARN_ON(1);
-		}
-		pm_runtime_put(vdev->device);
-		vfio_platform_regions_cleanup(vdev);
-		vfio_platform_irq_cleanup(vdev);
+	ret = vfio_platform_call_reset(vdev, &extra_dbg);
+	if (WARN_ON(ret && vdev->reset_required)) {
+		dev_warn(
+			vdev->device,
+			"reset driver is required and reset call failed in release (%d) %s\n",
+			ret, extra_dbg ? extra_dbg : "");
 	}
-
-	mutex_unlock(&driver_lock);
+	pm_runtime_put(vdev->device);
+	vfio_platform_regions_cleanup(vdev);
+	vfio_platform_irq_cleanup(vdev);
 }
 
-static int vfio_platform_open(struct vfio_device *core_vdev)
+static int vfio_platform_open_device(struct vfio_device *core_vdev)
 {
 	struct vfio_platform_device *vdev =
 		container_of(core_vdev, struct vfio_platform_device, vdev);
+	const char *extra_dbg = NULL;
 	int ret;
 
-	mutex_lock(&driver_lock);
-
-	if (!vdev->refcnt) {
-		const char *extra_dbg = NULL;
-
-		ret = vfio_platform_regions_init(vdev);
-		if (ret)
-			goto err_reg;
+	ret = vfio_platform_regions_init(vdev);
+	if (ret)
+		return ret;
 
-		ret = vfio_platform_irq_init(vdev);
-		if (ret)
-			goto err_irq;
+	ret = vfio_platform_irq_init(vdev);
+	if (ret)
+		goto err_irq;
 
-		ret = pm_runtime_get_sync(vdev->device);
-		if (ret < 0)
-			goto err_rst;
+	ret = pm_runtime_get_sync(vdev->device);
+	if (ret < 0)
+		goto err_rst;
 
-		ret = vfio_platform_call_reset(vdev, &extra_dbg);
-		if (ret && vdev->reset_required) {
-			dev_warn(vdev->device, "reset driver is required and reset call failed in open (%d) %s\n",
-				 ret, extra_dbg ? extra_dbg : "");
-			goto err_rst;
-		}
+	ret = vfio_platform_call_reset(vdev, &extra_dbg);
+	if (ret && vdev->reset_required) {
+		dev_warn(
+			vdev->device,
+			"reset driver is required and reset call failed in open (%d) %s\n",
+			ret, extra_dbg ? extra_dbg : "");
+		goto err_rst;
 	}
-
-	vdev->refcnt++;
-
-	mutex_unlock(&driver_lock);
 	return 0;
 
 err_rst:
 	pm_runtime_put(vdev->device);
 	vfio_platform_irq_cleanup(vdev);
 err_irq:
 	vfio_platform_regions_cleanup(vdev);
-err_reg:
-	mutex_unlock(&driver_lock);
 	return ret;
 }
 
@@ -616,8 +601,8 @@ static int vfio_platform_mmap(struct vfio_device *core_vdev, struct vm_area_stru
 
 static const struct vfio_device_ops vfio_platform_ops = {
 	.name		= "vfio-platform",
-	.open		= vfio_platform_open,
-	.release	= vfio_platform_release,
+	.open_device	= vfio_platform_open_device,
+	.close_device	= vfio_platform_close_device,
 	.ioctl		= vfio_platform_ioctl,
 	.read		= vfio_platform_read,
 	.write		= vfio_platform_write,

drivers/vfio/platform/vfio_platform_private.h

@@ -48,7 +48,6 @@ struct vfio_platform_device {
 	u32				num_regions;
 	struct vfio_platform_irq	*irqs;
 	u32				num_irqs;
-	int				refcnt;
 	struct mutex			igate;
 	const char			*compat;
 	const char			*acpihid;