Commit ff806cbd authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

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: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarShameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v4-c841817a0349+8f-vfio_get_from_dev_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 91be0bd6

drivers/vfio/pci/vfio_pci.c

+3 −1
Original line number Diff line number Diff line
@@ -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[] = {

drivers/vfio/pci/vfio_pci_core.c

+6 −26
Original line number Diff line number Diff line
@@ -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 @@ int vfio_pci_core_sriov_configure(struct pci_dev *pdev, int nr_virtfn) 
	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);

drivers/vfio/vfio.c

+1 −40
Original line number Diff line number Diff line
@@ -473,31 +473,15 @@ static void vfio_group_get(struct vfio_group *group) 
	refcount_inc(&group->users);

}



static struct vfio_group *vfio_group_get_from_dev(struct device *dev)

{

	struct iommu_group *iommu_group;

	struct vfio_group *group;



	iommu_group = iommu_group_get(dev);

	if (!iommu_group)

		return NULL;



	group = vfio_group_get_from_iommu(iommu_group);

	iommu_group_put(iommu_group);



	return group;

}



/*

 * Device objects - create, release, get, put, search

 */

/* Device reference always implies a group reference */

void vfio_device_put(struct vfio_device *device)

static void vfio_device_put(struct vfio_device *device)

{

	if (refcount_dec_and_test(&device->refcount))

		complete(&device->comp);

}

EXPORT_SYMBOL_GPL(vfio_device_put);



static bool vfio_device_try_get(struct vfio_device *device)

{
@@ -831,29 +815,6 @@ int vfio_register_emulated_iommu_dev(struct vfio_device *device) 
}

EXPORT_SYMBOL_GPL(vfio_register_emulated_iommu_dev);



/*

 * Get a reference to the vfio_device for a device.  Even if the

 * caller thinks they own the device, they could be racing with a

 * release call path, so we can't trust drvdata for the shortcut.

 * Go the long way around, from the iommu_group to the vfio_group

 * to the vfio_device.

 */

struct vfio_device *vfio_device_get_from_dev(struct device *dev)

{

	struct vfio_group *group;

	struct vfio_device *device;



	group = vfio_group_get_from_dev(dev);

	if (!group)

		return NULL;



	device = vfio_group_get_device(group, dev);

	vfio_group_put(group);



	return device;

}

EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);



static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,

						     char *buf)

{

include/linux/vfio.h

+0 −2
Original line number Diff line number Diff line
@@ -125,8 +125,6 @@ void vfio_uninit_group_dev(struct vfio_device *device); 
int vfio_register_group_dev(struct vfio_device *device);

int vfio_register_emulated_iommu_dev(struct vfio_device *device);

void vfio_unregister_group_dev(struct vfio_device *device);

extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);

extern void vfio_device_put(struct vfio_device *device);



int vfio_assign_device_set(struct vfio_device *device, void *set_id);

include/linux/vfio_pci_core.h

+2 −1
Original line number Diff line number Diff line
@@ -227,8 +227,9 @@ void vfio_pci_core_init_device(struct vfio_pci_core_device *vdev, 
int vfio_pci_core_register_device(struct vfio_pci_core_device *vdev);

void vfio_pci_core_uninit_device(struct vfio_pci_core_device *vdev);

void vfio_pci_core_unregister_device(struct vfio_pci_core_device *vdev);

int vfio_pci_core_sriov_configure(struct pci_dev *pdev, int nr_virtfn);

extern const struct pci_error_handlers vfio_pci_core_err_handlers;

int vfio_pci_core_sriov_configure(struct vfio_pci_core_device *vdev,

				  int nr_virtfn);

long vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int cmd,

		unsigned long arg);

int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags,