Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory

[Sagi Grimberg]

> Hi Everyone,

Hi Logan,

> Here's v2 of our series to introduce P2P based copy offload to NVMe
> fabrics. This version has been rebased onto v4.16-rc3 which already
> includes Christoph's devpagemap work the previous version was based
> off as well as a couple of the cleanup patches that were in v1.
>
> Additionally, we've made the following changes based on feedback:
>
> * Renamed everything to 'p2pdma' per the suggestion from Bjorn as well
>    as a bunch of cleanup and spelling fixes he pointed out in the last
>    series.
>
> * To address Alex's ACS concerns, we change to a simpler method of
>    just disabling ACS behind switches for any kernel that has
>    CONFIG_PCI_P2PDMA.
>
> * We also reject using devices that employ 'dma_virt_ops' which should
>    fairly simply handle Jason's concerns that this work might break with
>    the HFI, QIB and rxe drivers that use the virtual ops to implement
>    their own special DMA operations.

That's good, but what would happen for these devices? simply fail the
mapping causing the ulp to fail its rdma operation? I would think
that we need a capability flag for devices that support it.