Hi Mark,

On 1/15/2016 9:56 AM, Mark Rutland wrote:

Hi,

[adding KVM people, given this is meant for virtualization]

On Mon, Jan 11, 2016 at 09:45:43AM -0500, Sinan Kaya wrote:

quoted

The Qualcomm Technologies HIDMA device has been designed to support
virtualization technology. The driver has been divided into two to follow
the hardware design.

1. HIDMA Management driver
2. HIDMA Channel driver

Each HIDMA HW consists of multiple channels. These channels share some set
of common parameters. These parameters are initialized by the management
driver during power up. Same management driver is used for monitoring the
execution of the channels. Management driver can change the performance
behavior dynamically such as bandwidth allocation and prioritization.

The management driver is executed in hypervisor context and is the main
management entity for all channels provided by the device.

You mention repeatedly that this is designed for virtualization, but
looking at the series as it stands today I can't see how this operates
from the host side.

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. 

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. 

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. 

I just rely on the platform VFIO driver to do the work. 

Thanks,
Mark.

Sinan