| Message ID | 1491225304-3559-2-git-send-email-jnair@caviumnetworks.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On 03/04/17 14:15, Jayachandran C wrote: > Add a new quirk flag PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT to limit the DMA > alias search to go no further than the bridge where the IOMMU unit is > attached. > > The flag will be used to indicate a bridge device which forwards the > address translation requests to the IOMMU, i.e where the interrupt and > DMA requests leave the PCIe hierarchy and go into the system blocks. > > Usually this happens at the PCI RC, so this flag is not needed. But > on systems where there are bridges that introduce aliases above the > "real" root bridge, this flag is needed to ensure that the function > pci_for_each_dma_alias() works correctly. > > The function pci_for_each_dma_alias() is updated to stop when it see a > bridge with this flag set. As it seems to have been me positing most of the alternative suggestions, which have indeed turned out to have holes in (no, I can't see how we'd cleanly fix pci_device_group() either), I'll stand by my earlier "(I have no actual objection to this patch, though, [...])": Reviewed-by: Robin Murphy <robin.murphy@arm.com> > Signed-off-by: Jayachandran C <jnair@caviumnetworks.com> > --- > drivers/pci/search.c | 4 ++++ > include/linux/pci.h | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/drivers/pci/search.c b/drivers/pci/search.c > index 33e0f03..4c6044a 100644 > --- a/drivers/pci/search.c > +++ b/drivers/pci/search.c > @@ -60,6 +60,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, > > tmp = bus->self; > > + /* stop at bridge where translation unit is associated */ > + if (tmp->dev_flags & PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT) > + return ret; > + > /* > * PCIe-to-PCI/X bridges alias transactions from downstream > * devices using the subordinate bus number (PCI Express to > diff --git a/include/linux/pci.h b/include/linux/pci.h > index eb3da1a..3f596ac 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -178,6 +178,8 @@ enum pci_dev_flags { > PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), > /* Get VPD from function 0 VPD */ > PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), > + /* a non-root bridge where translation occurs, stop alias search here */ > + PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT = (__force pci_dev_flags_t) (1 << 9), > }; > > enum pci_irq_reroute_variant { >
diff --git a/drivers/pci/search.c b/drivers/pci/search.c index 33e0f03..4c6044a 100644 --- a/drivers/pci/search.c +++ b/drivers/pci/search.c @@ -60,6 +60,10 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, tmp = bus->self; + /* stop at bridge where translation unit is associated */ + if (tmp->dev_flags & PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT) + return ret; + /* * PCIe-to-PCI/X bridges alias transactions from downstream * devices using the subordinate bus number (PCI Express to diff --git a/include/linux/pci.h b/include/linux/pci.h index eb3da1a..3f596ac 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -178,6 +178,8 @@ enum pci_dev_flags { PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7), /* Get VPD from function 0 VPD */ PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8), + /* a non-root bridge where translation occurs, stop alias search here */ + PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT = (__force pci_dev_flags_t) (1 << 9), }; enum pci_irq_reroute_variant {
Add a new quirk flag PCI_DEV_FLAGS_BRIDGE_XLATE_ROOT to limit the DMA alias search to go no further than the bridge where the IOMMU unit is attached. The flag will be used to indicate a bridge device which forwards the address translation requests to the IOMMU, i.e where the interrupt and DMA requests leave the PCIe hierarchy and go into the system blocks. Usually this happens at the PCI RC, so this flag is not needed. But on systems where there are bridges that introduce aliases above the "real" root bridge, this flag is needed to ensure that the function pci_for_each_dma_alias() works correctly. The function pci_for_each_dma_alias() is updated to stop when it see a bridge with this flag set. Signed-off-by: Jayachandran C <jnair@caviumnetworks.com> --- drivers/pci/search.c | 4 ++++ include/linux/pci.h | 2 ++ 2 files changed, 6 insertions(+)