On 15/01/16 17:16, Sinan Kaya wrote: >>>> 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. Then may I suggest you both synchronize your submissions? I'd really like to hear from the QEMU maintainers that they are satisfied with that side of the story as well. Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
