On Tue, Jul 01, 2025 at 01:28:59PM -0600, Alex Williamson wrote:
> > +enum pci_bus_isolation pci_bus_isolated(struct pci_bus *bus)
> > +{
> > + struct pci_dev *bridge = bus->self;
> > + int type;
> > +
> > + /* Consider virtual busses isolated */
> > + if (!bridge)
> > + return PCIE_ISOLATED;
> > + if (pci_is_root_bus(bus))
> > + return PCIE_ISOLATED;
>
> How do we know the root bus isn't conventional?
If I read this right this is dead code..
/*
* Returns true if the PCI bus is root (behind host-PCI bridge),
* false otherwise
*
* Some code assumes that "bus->self == NULL" means that bus is a root bus.
* This is incorrect because "virtual" buses added for SR-IOV (via
* virtfn_add_bus()) have "bus->self == NULL" but are not root buses.
*/
static inline bool pci_is_root_bus(struct pci_bus *pbus)
{
return !(pbus->parent);
Looking at the call chain of pci_alloc_bus():
pci_alloc_child_bus() - Parent bus may not be NULL
pci_add_new_bus() - All callers pass !NULL bus
pci_register_host_bridge() - Sets self and parent to NULL
Thus if pci_is_root() == true implies bus->self == NULL so we can't
get here.
So I will change it to be like:
/*
* This bus was created by pci_register_host_bridge(). There is nothing
* upstream of this, assume it contains the TA and that the root complex
* does not allow P2P without going through the IOMMU.
*/
if (pci_is_root_bus(bus))
return PCIE_ISOLATED;
/*
* Sometimes SRIOV VFs can have a "virtual" bus if the SRIOV RID's
* extend past the bus numbers of the parent. The spec says that SRIOV
* VFs and PFs should act the same as functions in a MFD. MFD isolation
* is handled outside this function.
*/
if (!bridge)
return PCIE_ISOLATED;
And now it seems we never took care with SRIOV, along with the PF
every SRIOV VF needs to have its ACS checked as though it was a MFD..
Jason
