[dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for external memory

[Burakov, Anatoly]

On 14-Feb-19 1:41 PM, Shahaf Shuler wrote:
> Thursday, February 14, 2019 2:22 PM, Alejandro Lucero:
> 
>  >Any current NIC or device will work with virtual addresses if IOMMU is 
> in place, not matter if the device is  IOMMU-aware or not.
> 
> Not sure what you mean here. For example Intel devices works w/ VFIO and 
> use iova to provide buffers to NIC. hence protection between multiple 
> process is by application responsibility or new VFIO container.
> 

As far as VFIO is concerned, "multiprocess protection" is not a thing, 
because the device cannot be used twice in the first place - each usage 
is strictly limited to one VFIO container. We just sidestep this 
"limitation" by sharing container/device file descriptors with multiple 
processes via IPC.

So while it's technically true that multiprocess protection is 
"application responsibility" because we can pass around fd's, it's still 
protected by the kernel. IOVA mappings are per-container, so the same 
IOVA range can be mapped twice (thrice...), as long as it's for a 
different set of devices, in effect making them virtual addresses.

-- 
Thanks,
Anatoly