>>> This doesn't seem to tie into KVM or VFIO, and as far as I can tell >>> there's no mechanism for associating channels with a particular virtual >>> address space (i.e. no configuration of an external or internal IOMMU), >>> nor pinning of guest pages to allow for DMA to occur safely. >> >> I'm using VFIO platform driver for this purpose. VFIO platform driver is >> capable of assigning any platform device to a guest machine with this driver. > > Typically VFIO-platform also comes with a corresponding reset driver. > You don't need one? The HIDMA channel driver resets the channel before using it. That's why, I never bothered with writing a reset driver on the hypervisor. > >> You just unbind the HIDMA channel driver from the hypervisor and bind to vfio >> driver using the very same approach you'd use with PCIe. >> >> Of course, this all assumes the presence of an IOMMU driver on the system. VFIO >> driver uses the IOMMU driver to create the mappings. > > No IOMMU was described in the DT binding. It sounds like you'd need an > optional (not present in the guest) iommus property per-channel You are right. I missed that part. I'll update the device-tree binding documentation. > >> The mechanism used here is not different from VFIO PCI from user perspective. >> >>> >>> Given that, I'm at a loss as to how this would be used in a hypervisor >>> context. What am I missing? >>> >>> Are there additional patches, or do you have some userspace that works >>> with this in some limited configuration? >> >> No, these are the only patches. We have one patch for the QEMU but from kernel >> perspective this is it. > > Do you have a link to that? Seeing it would help to ease my concerns. The QEMU driver has not been posted yet. As far as I know, it just discovers the memory resources on the platform object and creates mappings for the guest machine only. Shanker Donthineni and Vikram Sethi will post the QEMU patch later. > > Thanks, > Mark. > -- Sinan Kaya Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
