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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>
This commit is contained in:
Jason Gunthorpe 2022-05-11 13:19:07 -06:00 committed by Alex Williamson
parent 91be0bd6c6
commit ff806cbd90
5 changed files with 12 additions and 70 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/vfio/pci/vfio_pci.c
View File

@ -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[] = {

32
drivers/vfio/pci/vfio_pci_core.c
View File

@ -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);

41
drivers/vfio/vfio.c
View File

@ -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)
{

2
include/linux/vfio.h
View File

@ -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);

3
include/linux/vfio_pci_core.h
View File

@ -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,