On Wed, Nov 06, 2013 at 11:56:13AM -0800, Yinghai Lu wrote:
> On Wed, Nov 6, 2013 at 10:15 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
>
> > commit dfb66fee4715c747a94abd45c20fbe302b10e49c
> > Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Date: Wed Nov 6 10:11:48 2013 -0700
> >
> > PCI: Add pci_upstream_bridge()
> >
> > This adds a pci_upstream_bridge() interface to find the PCI-to-PCI bridge
> > upstream from a device. If the device is on a root bus, i.e., the upstream
> > bridge is a host bridge instead of a PCI bridge, this returns NULL. If the
> > device is a VF, this returns the bridge upstream from the PF corresponding
> > to the VF. This is important for VFs on virtual buses, where
> > "dev->bus->self == NULL".
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> >
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index d3a888a..e09d19a 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -480,6 +480,18 @@ static inline bool pci_is_root_bus(struct pci_bus *pbus)
> > return !(pbus->parent);
> > }
> >
> > +static inline struct pci_dev *pci_upstream_bridge(struct pci_dev *dev)
> > +{
> > + if (pci_is_root_bus(dev->bus))
> > + return NULL;
> > +
> > + dev = pci_physfn(dev);
> > + if (pci_is_root_bus(dev->bus))
> > + return NULL;
>
> Maybe we can drop the first pci_is_root_bus() checking.
> for physfn, pci_physfn will return it's self.
Yep, that makes sense, thanks. I incorporated that change.
> > +
> > + return dev->bus->self;
> > +}
> > +
> > #ifdef CONFIG_PCI_MSI
> > static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev)
> > {
> > commit 4e5415f02e32c85e902cd9692eab18200e14b347
> > Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Date: Wed Nov 6 10:00:51 2013 -0700
> >
> > PCI: Enable upstream bridges even for VFs on virtual buses
> >
> > Previously we enabled the upstream PCI-to-PCI bridge only when
> > "dev->bus->self != NULL". In the case of a VF on a virtual bus, where
> > "bus->self == NULL", we didn't enable the upstream bridge.
> >
> > This fixes that by enabling the upstream bridge of the PF corresponding to
> > the VF.
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index ac40f90..744dc26 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1150,10 +1150,8 @@ static void pci_enable_bridge(struct pci_dev *dev)
> > {
> > int retval;
> >
> > - if (!dev)
> > - return;
> > -
> > - pci_enable_bridge(dev->bus->self);
> > + if (!pci_is_root_bus(dev->bus))
> > + pci_enable_bridge(pci_upstream_bridge(dev));
> >
> > if (pci_is_enabled(dev)) {
> > if (!dev->is_busmaster)
> > @@ -1188,7 +1186,8 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
> > if (atomic_inc_return(&dev->enable_cnt) > 1)
> > return 0; /* already enabled */
> >
> > - pci_enable_bridge(dev->bus->self);
> > + if (!pci_is_root_bus(dev->bus))
> > + pci_enable_bridge(pci_upstream_bridge(dev));
> >
> > /* only skip sriov related */
> > for (i = 0; i <= PCI_ROM_RESOURCE; i++)
>
> still have problem.
>
> pci_upstream_bridge() could return NULL. so later pci_enable_bridge()
> referring dev->bus could panic, as you remove !dev checking.
pci_upstream_bridge(dev) can only return NULL if dev is on a root bus,
and we never call pci_enable_bridge() in that case. So I don't see
the problem.
Bjorn
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