From: Greg Kurz groug@kaod.org
commit 02c5f5394918b9b47ff4357b1b18335768cd867d upstream.
Since 902bdc57451c, get_pci_dev() calls pci_get_domain_bus_and_slot(). This has the effect of incrementing the reference count of the PCI device, as explained in drivers/pci/search.c:
* Given a PCI domain, bus, and slot/function number, the desired PCI * device is located in the list of PCI devices. If the device is * found, its reference count is increased and this function returns a * pointer to its data structure. The caller must decrement the * reference count by calling pci_dev_put(). If no device is found, * %NULL is returned.
Nothing was done to call pci_dev_put() and the reference count of GPU and NPU PCI devices rockets up.
A natural way to fix this would be to teach the callers about the change, so that they call pci_dev_put() when done with the pointer. This turns out to be quite intrusive, as it affects many paths in npu-dma.c, pci-ioda.c and vfio_pci_nvlink2.c. Also, the issue appeared in 4.16 and some affected code got moved around since then: it would be problematic to backport the fix to stable releases.
All that code never cared for reference counting anyway. Call pci_dev_put() from get_pci_dev() to revert to the previous behavior.
Fixes: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn") Cc: stable@vger.kernel.org # v4.16 Signed-off-by: Greg Kurz groug@kaod.org Reviewed-by: Alexey Kardashevskiy aik@ozlabs.ru Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/platforms/powernv/npu-dma.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
--- a/arch/powerpc/platforms/powernv/npu-dma.c +++ b/arch/powerpc/platforms/powernv/npu-dma.c @@ -31,9 +31,22 @@ static DEFINE_SPINLOCK(npu_context_lock) static struct pci_dev *get_pci_dev(struct device_node *dn) { struct pci_dn *pdn = PCI_DN(dn); + struct pci_dev *pdev;
- return pci_get_domain_bus_and_slot(pci_domain_nr(pdn->phb->bus), + pdev = pci_get_domain_bus_and_slot(pci_domain_nr(pdn->phb->bus), pdn->busno, pdn->devfn); + + /* + * pci_get_domain_bus_and_slot() increased the reference count of + * the PCI device, but callers don't need that actually as the PE + * already holds a reference to the device. Since callers aren't + * aware of the reference count change, call pci_dev_put() now to + * avoid leaks. + */ + if (pdev) + pci_dev_put(pdev); + + return pdev; }
/* Given a NPU device get the associated PCI device. */