[ofa-general] [PATCH RFC v3 1/2] RDMA/Core: MEM_MGT_EXTENSIONS support

[Or Gerlitz]

Steve Wise wrote:
> - device-specific alloc/free of physical buffer lists for use in fast
> register work requests.  This allows devices to allocate this memory as
> needed (like via dma_alloc_coherent).
>
Steve,

Reading through the suggested API / patches and the previous threads I 
was not sure to understand if the HW driver must not assume that it has 
the ownership on the page --list-- structure until the registration work 
request is completed - or not.

Now, if ownership can not be assumed (eg as for the SG list elements 
pointed by send/recv WR), the driver has to clone it anyway, and thus I 
don't see the need in the ib_alloc/free_fast_reg_page_list verbs.

If ownership can be assumed, I suggest to have the core use the 
implementation of these two verbs as you did that for the Chelsio driver 
in case the HW driver did not implement it (i.e instead of returning 
ENOSYS). In that case, the alloc_list verb should do DMA mapping FROM 
device (I think...) since the device is going to do DMA to read the page 
list, and the free_list verb should do DMA unmapping, etc.

Or.