On Wed, 2013-04-03 at 14:09 -0500, Stuart Yoder wrote: > > Would is be possible for userspace to simply leave room for MSI bank > > mapping (how much room could be determined by something like > > VFIO_IOMMU_GET_MSI_BANK_COUNT) then document the API that userspace can > > DMA_MAP starting at the 0x0 address of the aperture, growing up, and > > VFIO will map banks on demand at the top of the aperture, growing down? > > Wouldn't that avoid a lot of issues with userspace needing to know > > anything about MSI banks (other than count) and coordinating irq numbers > > and enabling handlers? > > This is basically option #A in the original proposals sent. I like > this approach, in that it > is simpler and keeps user space mostly out of this...which is > consistent with how things are done > on x86. User space just needs to know how many windows to leave at > the top of the aperture. > The kernel then has the flexibility to use those windows how it wants. > > But one question, is when should the kernel actually map (and unmap) > the MSI banks. One thing we need to do is enable the aperture...and current > thinking is that is done on the first DMA_MAP. Similarly when the last > mapping > is unmapped we could also umap the MSI banks. > > Sequence would be something like: > > VFIO_GROUP_SET_CONTAINER // add groups to the container > > VFIO_SET_IOMMU(VFIO_FSL_PAMU) // set iommu model > > cnt = VFIO_IOMMU_GET_MSI_BANK_COUNT // returns max # of MSI banks > > VFIO_IOMMU_SET_ATTR(ATTR_GEOMETRY) // set overall aperture > > VFIO_IOMMU_SET_ATTR(ATTR_WINDOWS) // set # of windows, > including MSI banks > > VFIO_IOMMU_MAP_DMA // map the guest's memory > ---> kernel enables aperture and maps needed MSI banks here > > VFIO_DEVICE_SET_IRQS > ---> kernel sets actual MSI addr/data in physical > device here (I think)
You could also make use of the IOMMU_ENABLE/DISABLE entry points that Alexey plans to use. Ideally I'd think that you'd want to enable the required MSI banks for a device on DEVICE_SET_IRQs. That's effectively what happens on x86. Perhaps some information stored in the domain structure would let architecture hooks in MSI setup enable those mappings for you? Thanks, Alex _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
