On Thu, 2014-05-15 at 07:40 +0800, Andrew Cooks wrote: > Hi Alex > > On Fri, May 9, 2014 at 11:28 PM, Alex Williamson > <alex.williamson@xxxxxxxxxx> wrote: > > .... > > > > Original description: > > > > This series attempts to fix a couple issues we've had outstanding in > > the PCI/IOMMU code for a while. The first issue is with devices that > > use the wrong requester ID for DMA transactions. We already have a > > sort of half-baked attempt to fix this for several Ricoh devices, but > > the fix only helps them be useful through IOMMU groups, not the > > general DMA case. There are also several Marvell devices which use > > use a different wrong requester ID and don't even fit into the DMA > > source idea. This series creates a DMA alias iterator that will > > step through each possible alias of a device, allowing IOMMUs to > > insert mappings for both the device and its aliases. > > > > Hand-in-hand with this is our broken pci_find_upstream_pcie_bridge() > > function, which is known to blowup when it finds itself suddenly at > > a PCIe device without crossing a PCIe-to-PCI bridge (as identified by > > the PCIe capability). It also likes to make the invalid assumption > > that a PCIe device never has its requester ID masked by any usptream > > bus. We can fix this using the above new DMA alias iterator, since > > that's effectively what this function was meant to do. > > > > There are two cases where the DMA requester id seems to use the wrong > slot (as opposed to function) in the patch I attached to > https://bugzilla.kernel.org/show_bug.cgi?id=42679 > The original bug reports are listed in the patch. > > Unfortunately, I wasn't able to get test feedback on those two cases, > but I'm wondering... > Did I understand correctly that a slot alias is something that could be needed? > If so, is it a variation of the PCIe-to-PCI bridge case that's already > covered or will it require a different approach? Wow, I didn't think that kind of broken was possible. Maybe instead of a bitmap of function aliases we could have a single devfn alias for a device. That means we'd only be able to support a single alias for a device, but since I don't think we've seen devices that use more than a single alias, maybe that's ok. I'll see what changes we'd need to make for that, but I probably won't go adding the actual quirk based on those old reports. Thanks, Alex -- 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
