On Mon, Aug 02, 2010 at 09:58:02AM +0200, Roedel, Joerg wrote: > Hi Stephan, > > On Fri, Jul 30, 2010 at 01:19:06AM -0400, stepanm@xxxxxxxxxxxxxx wrote: > > Unlike a more traditional system with one IOMMU between the bus and > > memory, MSM has multiple IOMMUs, with each one hard-wired to a dedicated > > device. Furthermore, each IOMMU can have more than one translation > > context. One of the use cases is being able to create mappings within > > multiple instances of one context, and arbitrarily context-switch the > > IOMMU on the fly. > > The IOMMU-API supports multiple IOMMUs (at least multiple AMD/Intel > IOMMUs). But the face that there are more than one IOMMU is hidden in > the backend driver implementation. The API itself only works with > domains and devices. The IOMMU driver needs to know which IOMMU it needs > to program for a given device. If I understand the concept of your > hardware correctly you also have this information. > > > It sounds like the domain abstraction and attach_device/detach_device can > > encapsulate this rather nicely and I am in the process of updating my > > driver to fit this framework. > > > > My problem, however, is with iommu_domain_alloc(). This will set up a > > domain and call the ops function to initialize it, but I want to be able > > to pass it an ???IOMMU id" that will tell the underlying driver which IOMMU > > (and which "stream id") is to be associated with that domain instance. > > This can be a void* parameter that gets passed through to domain_init. I > > feel like this change will make it easy to deal with multiple > > IOMMUs/translation contexts, and implementations that have only a singular > > IOMMU/translation context are free to ignore that parameter. > > In the means of the IOMMU-API the domain is the abstraction of an > address space (in other words a page table). The IOMMU(s) which this domain > is later assigned to are determined by the iommu_attach_device calls. > I think the right way to go here is to create the concept of a > device-context in the IOMMU-API and add functions like > > iommu_attach_context(struct iommu_domain *domain, > struct iommu_context *ctxt); > iommu_detach_context(struct iommu_context *ctxt); > > This would work if you can determine in your iommu-driver which iommu > you need to program for which device. What do you think? > Joerg, I'd like to make sure I understand this. A domain is an address space separate from the actual page-tables that may be part of an iommu_context, correct? After I iommu_attach_context the ctxt will reflect the address space of the domain, correct? > > Joerg > > -- > Joerg Roedel - AMD Operating System Research Center > > Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach > General Managers: Alberto Bozzo, Andrew Bowd > Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
