Hi Alex On Fri, May 16, 2014 at 1:43 AM, Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > 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. The current patch creates a context entry for the reported device (function 0), plus it's alias (function 1). Is there reason to always add a context entry for the reported devfn and define 'alias' to mean 'one additional devfn'? That will work for all the Marvell cases. In the testing I did, the Marvell controllers needed context entries for both function 0 and 1. It would be nice if someone could confirm or debunk this. I tested with a 88SE9172 with both ports of the controller in use. Thanks, a. -- 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
