[RFC 7/7] NVMe: CMB on DMA-BUF

[Haggai Eran]

On 8/4/2016 2:56 PM, hch at infradead.org wrote:
>> Anyway, I understand exposing the CMB directly might be a little too
>> low level. What do you think would work better? Something like
>> direct_access that returns bus addresses instead of pfns?
> 
> This would be my primary choicse.  We'll really need to built an
> in-kernel framework for a) PCI P2P access involving drivers for the PCI
> switches etc, 
I was thinking perhaps the dma_map_resource patches by Will Davis [1]
could be used (adding him to the thread).

> and then on top of that build something speicifly for
> block drivers.  Which will be a bit complicated because both have the
> case of directly memory mapped device as well as indirect devices like
> the CMB.  I'm pretty sure we won't get it right at the first attempt,
> so exposing it to userspace is an absolute no-go as that will lock us
> into the first ABI forever.
I understand. I'll try to think of something for kernel usage only for
the next attempt.

Thanks,
Haggai

[1]
https://lists.linuxfoundation.org/pipermail/iommu/2015-August/014106.html