On 14/11/16 10:26, Lorenzo Pieralisi wrote: > Hi Robin, Joerg, > > On Fri, Nov 11, 2016 at 05:43:39PM +0000, Robin Murphy wrote: >> On 11/11/16 16:27, Joerg Roedel wrote: >>> On Fri, Nov 11, 2016 at 04:17:37PM +0000, Robin Murphy wrote: >>>> In the original of_iommu_configure design, the thought was that an ops >>>> structure could be IOMMU-instance-specific (hence the later-removed >>>> "priv" member), so I suppose right now it is mostly a hangover from >>>> that. However, it's also what we initialise a device's fwspec with, so >>>> becomes important again if we're ever going to get past the limitations >>>> of buses-which-are-not-actually-buses[1]. >>> >>> Yeah, I discussed this with a few others at LPC. My current idea is to >>> tell the iommu-core which hardware-iommus exist in the system and a >>> seperate iommu_ops ptr for each of them. Then every struct device can >>> link to the iommu-instance it is translated by. >> >> Er, that sounds very much like a description of what we already have in >> 4.9-rc. Every struct device now has an iommu_fwspec which encapsulates >> both an iommu_ops pointer (which can perfectly well be per-instance if >> the IOMMU driver wants) and a place for the IOMMU-private data to >> replace the mess of archdata.iommu and driver-internal globals. >> >>> We are not there yet, but this will give you the same per-device >>> iommu-ops as implemented here. >> >> With those two patches I linked to, which make the bulk of the IOMMU >> core code per-device-ops-aware off the bat, I'd say we *are* already >> pretty much there. It's only iommu_domain_alloc() which needs a >> device-based alternative, and the non-of_xlate-based IOMMU drivers to >> either call iommu_fwspec_init() for themselves, or perhaps for x86 >> plumbing in DMAR/IVRS equivalents of the IORT parsing to the >> infrastructure provided by this series. > > I think it all boils down to how we end up implementing the per-device > iommu_ops look-up/binding, question is what do you want me to do with > this patch, it should be fine to drop it and use dev->bus->iommu_ops > for the look-up but I should know sooner rather than later to make > sure the series get another good round of testing. If we've already made the decision to move away from bus ops, I don't see that it makes sense to deliberately introduce new dependencies on them. Besides, as it stands, this patch literally implements "tell the iommu-core which hardware-iommus exist in the system and a seperate iommu_ops ptr for each of them" straight off. Robin. > > Please let me know, thank you very much. > > Lorenzo > -- 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
