On Thu, 3 Mar 2016 15:38:02 +0100 Jacek Lawrynowicz <jacek.lawrynowicz@xxxxxxxxx> wrote: > This patch solves IOMMU support issues with PCIe non-transparent bridges > that use Requester ID look-up tables (RID-LUT), e.g. PEX8733. > > The NTB connects devices in two independent PCI domains. Devices > separated by the NTB are not able to discover each other. A PCI packet > being forwared from one domain to another has to have its RID modified > so it appears on correct bus and completions are forwarded back to the > original domain through the NTB. RID is translated using preprogrammed > table (LUT) and the PCI packet propagates upstream away from the NTB. > If the destination system has IOMMU enabled, the packet will be > discarded because the new RID is unknown to the IOMMU. Adding a DMA > alias for the new RID allows IOMMU to properly recognize the packet. > > Each device behind the NTB has a unique RID assigned in the RID-LUT. > Current DMA alias implementation supports only single alias, so it's not > possible to support mutiple devices behind the NTB when IOMMU is enabled. > > This implementation enables all possible aliases on a given bus (256) > that are stored in a bitset. Alias devfn is directly translated to a bit > number. The bitset is not allocated for devices that have no need for > DMA aliases. > > More details can be found in following article: > http://www.plxtech.com/files/pdf/technical/expresslane/RTC_Enabling%20MulitHostSystemDesigns.pdf > > Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@xxxxxxxxx> > Acked-by: David Woodhouse <David.Woodhouse@xxxxxxxxx> > Acked-by: Joerg Roedel <jroedel@xxxxxxx> > --- > I updated the commit message based on discussion with Bjorn. It should be > now a little easier to understand. I'm not resubmitting the whole patch set > because it could make the thread harder to follow. > > This time resubmitting with correct subject. > > drivers/iommu/iommu.c | 17 ++++++++++------- > drivers/pci/pci.c | 11 +++++++++-- > drivers/pci/probe.c | 1 + > drivers/pci/search.c | 14 +++++++++----- > include/linux/pci.h | 4 +--- > 5 files changed, 30 insertions(+), 17 deletions(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index bfd4f7c..4c10da1 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -659,9 +659,15 @@ static struct iommu_group *get_pci_function_alias_group(struct pci_dev *pdev, > return NULL; > } > > +static bool dma_alias_is_enabled(struct pci_dev *dev, u8 devfn) > +{ > + return dev->dma_alias_mask && > + test_bit(devfn, dev->dma_alias_mask); > +} > + > /* > - * Look for aliases to or from the given device for exisiting groups. The > - * dma_alias_devfn only supports aliases on the same bus, therefore the search > + * Look for aliases to or from the given device for existing groups. DMA > + * aliases are only supported on the same bus, therefore the search > * space is quite small (especially since we're really only looking at pcie > * device, and therefore only expect multiple slots on the root complex or > * downstream switch ports). It's conceivable though that a pair of > @@ -686,11 +692,8 @@ static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev, > continue; > > /* We alias them or they alias us */ > - if (((pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) && > - pdev->dma_alias_devfn == tmp->devfn) || > - ((tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) && > - tmp->dma_alias_devfn == pdev->devfn)) { > - > + if (dma_alias_is_enabled(pdev, tmp->devfn) || > + dma_alias_is_enabled(tmp, pdev->devfn)) { > group = get_pci_alias_group(tmp, devfns); > if (group) { > pci_dev_put(tmp); > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index e5e2c9d..33f3d24 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4577,8 +4577,15 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode, > */ > void pci_add_dma_alias(struct pci_dev *dev, u8 devfn) > { > - dev->dma_alias_devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0); > - dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN; > + if (!dev->dma_alias_mask) > + dev->dma_alias_mask = kcalloc(BITS_TO_LONGS(U8_MAX), > + sizeof(long), GFP_KERNEL); > + if (!dev->dma_alias_mask) { > + dev_warn(&dev->dev, "Unable to allocate DMA alias mask\n"); > + return; > + } > + > + set_bit(devfn, dev->dma_alias_mask); This silently fixes the bug in 1/, it should be updated after 1/ is fixed. Otherwise, Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > dev_info(&dev->dev, "Enabling fixed DMA alias to %02x.%d\n", > PCI_SLOT(devfn), PCI_FUNC(devfn)); > } > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 5eb378f..cf09307 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -1502,6 +1502,7 @@ static void pci_release_dev(struct device *dev) > pcibios_release_device(pci_dev); > pci_bus_put(pci_dev->bus); > kfree(pci_dev->driver_override); > + kfree(pci_dev->dma_alias_mask); > kfree(pci_dev); > } > > diff --git a/drivers/pci/search.c b/drivers/pci/search.c > index a20ce7d..33e0f03 100644 > --- a/drivers/pci/search.c > +++ b/drivers/pci/search.c > @@ -40,11 +40,15 @@ int pci_for_each_dma_alias(struct pci_dev *pdev, > * If the device is broken and uses an alias requester ID for > * DMA, iterate over that too. > */ > - if (unlikely(pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN)) { > - ret = fn(pdev, PCI_DEVID(pdev->bus->number, > - pdev->dma_alias_devfn), data); > - if (ret) > - return ret; > + if (unlikely(pdev->dma_alias_mask)) { > + u8 devfn; > + > + for_each_set_bit(devfn, pdev->dma_alias_mask, U8_MAX) { > + ret = fn(pdev, PCI_DEVID(pdev->bus->number, devfn), > + data); > + if (ret) > + return ret; > + } > } > > for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) { > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 614d70d..0c176e5 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -172,8 +172,6 @@ enum pci_dev_flags { > PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) (1 << 2), > /* Flag for quirk use to store if quirk-specific ACS is enabled */ > PCI_DEV_FLAGS_ACS_ENABLED_QUIRK = (__force pci_dev_flags_t) (1 << 3), > - /* Flag to indicate the device uses dma_alias_devfn */ > - PCI_DEV_FLAGS_DMA_ALIAS_DEVFN = (__force pci_dev_flags_t) (1 << 4), > /* Use a PCIe-to-PCI bridge alias even if !pci_is_pcie */ > PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 5), > /* Do not use bus resets for device */ > @@ -279,7 +277,7 @@ struct pci_dev { > u8 rom_base_reg; /* which config register controls the ROM */ > u8 pin; /* which interrupt pin this device uses */ > u16 pcie_flags_reg; /* cached PCIe Capabilities Register */ > - u8 dma_alias_devfn;/* devfn of DMA alias, if any */ > + unsigned long *dma_alias_mask;/* mask of enabled devfn aliases */ > > struct pci_driver *driver; /* which driver has allocated this device */ > u64 dma_mask; /* Mask of the bits of bus address this -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
