vfio/pci: Remove vfio_device_get_from_dev()

The last user of this function is in PCI callbacks that want to convert
their struct pci_dev to a vfio_device. Instead of searching use the
vfio_device available trivially through the drvdata.

When a callback in the device_driver is called, the caller must hold the
device_lock() on dev. The purpose of the device_lock is to prevent
remove() from being called (see __device_release_driver), and allow the
driver to safely interact with its drvdata without races.

The PCI core correctly follows this and holds the device_lock() when
calling error_detected (see report_error_detected) and
sriov_configure (see sriov_numvfs_store).

Further, since the drvdata holds a positive refcount on the vfio_device
any access of the drvdata, under the device_lock(), from a driver callback
needs no further protection or refcounting.

Thus the remark in the vfio_device_get_from_dev() comment does not apply
here, VFIO PCI drivers all call vfio_unregister_group_dev() from their
remove callbacks under the device_lock() and cannot race with the
remaining callers.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v4-c841817a0349+8f-vfio_get_from_dev_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

2 files changed, 9 insertions, 27 deletions

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 8c990a1a7def..cdee5f81f49d 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -174,10 +174,12 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 
 static int vfio_pci_sriov_configure(struct pci_dev *pdev, int nr_virtfn)
 {
+	struct vfio_pci_core_device *vdev = dev_get_drvdata(&pdev->dev);
+
 	if (!enable_sriov)
 		return -ENOENT;
 
-	return vfio_pci_core_sriov_configure(pdev, nr_virtfn);
+	return vfio_pci_core_sriov_configure(vdev, nr_virtfn);
 }
 
 static const struct pci_device_id vfio_pci_table[] = {
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 65587fd5c021..100ab98c7ff0 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1894,9 +1894,7 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_register_device);
 
 void vfio_pci_core_unregister_device(struct vfio_pci_core_device *vdev)
 {
-	struct pci_dev *pdev = vdev->pdev;
-
-	vfio_pci_core_sriov_configure(pdev, 0);
+	vfio_pci_core_sriov_configure(vdev, 0);
 
 	vfio_unregister_group_dev(&vdev->vdev);
 
@@ -1911,14 +1909,7 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_unregister_device);
 pci_ers_result_t vfio_pci_core_aer_err_detected(struct pci_dev *pdev,
 						pci_channel_state_t state)
 {
-	struct vfio_pci_core_device *vdev;
-	struct vfio_device *device;
-
-	device = vfio_device_get_from_dev(&pdev->dev);
-	if (device == NULL)
-		return PCI_ERS_RESULT_DISCONNECT;
-
-	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+	struct vfio_pci_core_device *vdev = dev_get_drvdata(&pdev->dev);
 
 	mutex_lock(&vdev->igate);
 
@@ -1927,26 +1918,18 @@ pci_ers_result_t vfio_pci_core_aer_err_detected(struct pci_dev *pdev,
 
 	mutex_unlock(&vdev->igate);
 
-	vfio_device_put(device);
-
 	return PCI_ERS_RESULT_CAN_RECOVER;
 }
 EXPORT_SYMBOL_GPL(vfio_pci_core_aer_err_detected);
 
-int vfio_pci_core_sriov_configure(struct pci_dev *pdev, int nr_virtfn)
+int vfio_pci_core_sriov_configure(struct vfio_pci_core_device *vdev,
+				  int nr_virtfn)
 {
-	struct vfio_pci_core_device *vdev;
-	struct vfio_device *device;
+	struct pci_dev *pdev = vdev->pdev;
 	int ret = 0;
 
 	device_lock_assert(&pdev->dev);
 
-	device = vfio_device_get_from_dev(&pdev->dev);
-	if (!device)
-		return -ENODEV;
-
-	vdev = container_of(device, struct vfio_pci_core_device, vdev);
-
 	if (nr_virtfn) {
 		mutex_lock(&vfio_pci_sriov_pfs_mutex);
 		/*
@@ -1964,8 +1947,7 @@ int vfio_pci_core_sriov_configure(struct pci_dev *pdev, int nr_virtfn)
 		ret = pci_enable_sriov(pdev, nr_virtfn);
 		if (ret)
 			goto out_del;
-		ret = nr_virtfn;
-		goto out_put;
+		return nr_virtfn;
 	}
 
 	pci_disable_sriov(pdev);
@@ -1975,8 +1957,6 @@ out_del:
 	list_del_init(&vdev->sriov_pfs_item);
 out_unlock:
 	mutex_unlock(&vfio_pci_sriov_pfs_mutex);
-out_put:
-	vfio_device_put(device);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(vfio_pci_core_sriov_configure);