Searched hist:a7e9f240c0da4fb73a353c603daf4beba04c6ecf (Results 1 – 2 of 2) sorted by relevance
| /linux/drivers/pci/ |
| H A D | iov.c | diff a7e9f240c0da4fb73a353c603daf4beba04c6ecf Thu Feb 24 15:20:13 CET 2022 Jason Gunthorpe <jgg@nvidia.com> PCI/IOV: Add pci_iov_get_pf_drvdata() to allow VF reaching the drvdata of a PF
There are some cases where a SR-IOV VF driver will need to reach into and
interact with the PF driver. This requires accessing the drvdata of the PF.
Provide a function pci_iov_get_pf_drvdata() to return this PF drvdata in a
safe way. Normally accessing a drvdata of a foreign struct device would be
done using the device_lock() to protect against device driver
probe()/remove() races.
However, due to the design of pci_enable_sriov() this will result in a
ABBA deadlock on the device_lock as the PF's device_lock is held during PF
sriov_configure() while calling pci_enable_sriov() which in turn holds the
VF's device_lock while calling VF probe(), and similarly for remove.
This means the VF driver can never obtain the PF's device_lock.
Instead use the implicit locking created by pci_enable/disable_sriov(). A
VF driver can access its PF drvdata only while its own driver is attached,
and the PF driver can control access to its own drvdata based on when it
calls pci_enable/disable_sriov().
To use this API the PF driver will setup the PF drvdata in the probe()
function. pci_enable_sriov() is only called from sriov_configure() which
cannot happen until probe() completes, ensuring no VF races with drvdata
setup.
For removal, the PF driver must call pci_disable_sriov() in its remove
function before destroying any of the drvdata. This ensures that all VF
drivers are unbound before returning, fencing concurrent access to the
drvdata.
The introduction of a new function to do this access makes clear the
special locking scheme and the documents the requirements on the PF/VF
drivers using this.
Link: https://lore.kernel.org/all/20220224142024.147653-5-yishaih@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
|
| /linux/include/linux/ |
| H A D | pci.h | diff a7e9f240c0da4fb73a353c603daf4beba04c6ecf Thu Feb 24 15:20:13 CET 2022 Jason Gunthorpe <jgg@nvidia.com> PCI/IOV: Add pci_iov_get_pf_drvdata() to allow VF reaching the drvdata of a PF
There are some cases where a SR-IOV VF driver will need to reach into and
interact with the PF driver. This requires accessing the drvdata of the PF.
Provide a function pci_iov_get_pf_drvdata() to return this PF drvdata in a
safe way. Normally accessing a drvdata of a foreign struct device would be
done using the device_lock() to protect against device driver
probe()/remove() races.
However, due to the design of pci_enable_sriov() this will result in a
ABBA deadlock on the device_lock as the PF's device_lock is held during PF
sriov_configure() while calling pci_enable_sriov() which in turn holds the
VF's device_lock while calling VF probe(), and similarly for remove.
This means the VF driver can never obtain the PF's device_lock.
Instead use the implicit locking created by pci_enable/disable_sriov(). A
VF driver can access its PF drvdata only while its own driver is attached,
and the PF driver can control access to its own drvdata based on when it
calls pci_enable/disable_sriov().
To use this API the PF driver will setup the PF drvdata in the probe()
function. pci_enable_sriov() is only called from sriov_configure() which
cannot happen until probe() completes, ensuring no VF races with drvdata
setup.
For removal, the PF driver must call pci_disable_sriov() in its remove
function before destroying any of the drvdata. This ensures that all VF
drivers are unbound before returning, fencing concurrent access to the
drvdata.
The introduction of a new function to do this access makes clear the
special locking scheme and the documents the requirements on the PF/VF
drivers using this.
Link: https://lore.kernel.org/all/20220224142024.147653-5-yishaih@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
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