On Mon, Jan 08, 2018 at 12:01:16PM -0700, Jason Gunthorpe wrote:
> > So I very much disagree about where to place that workaround - the
> > RDMA code is exactly the right place.
>
> But why? RDMA is using core code to do this. It uses dma_ops in struct
> device and it uses normal dma_map SG. How
On Mon, Jan 08, 2018 at 12:05:57PM -0700, Logan Gunthorpe wrote:
> Ok, so if we shouldn't touch the dma_map infrastructure how should the
> workaround to opt-out HFI and QIB look? I'm not that familiar with the RDMA
> code.
We can add a no_p2p quirk, I'm just not sure what the right place
for
On Mon, Jan 08, 2018 at 12:49:50PM -0700, Jason Gunthorpe wrote:
> Pretty sure P2P capable IOMMU hardware exists.
>
> With SOC's we also have the scenario that an DMA originated from an
> on-die device wishes to target an off-die PCI BAR (through the IOMMU),
> that definitely exists today, and
On Mon, Jan 08, 2018 at 11:44:41AM -0700, Logan Gunthorpe wrote:
>> Think about what the dma mapping routines do:
>>
>> (a) translate from host address to bus addresses
>>
>> and
>>
>> (b) flush caches (in non-coherent architectures)
>>
>> Both are obviously not needed for P2P transfers, as
On Mon, Jan 08, 2018 at 11:09:17AM -0700, Jason Gunthorpe wrote:
> > As usual we implement what actually has a consumer. On top of that the
> > R/W API is the only core RDMA API that actually does DMA mapping for the
> > ULP at the moment.
>
> Well again the same can be said for dma_map_page vs
On 08/01/18 11:09 AM, Jason Gunthorpe wrote:
It could, if we had a DMA op for p2p then the drivers that provide
their own ops can implement it appropriately or not at all.
I was thinking of doing something like this. I'll probably rough out a
patch and send it along today or tomorrow.
If
On Thu, Jan 04, 2018 at 09:50:31PM -0700, Jason Gunthorpe wrote:
> Well that argument applies equally to the RDMA RW API wrappers around
> the DMA API. I think it is fine if sgl are defined to only have P2P or
> not, and that debugging support seemed reasonable to me..
>
> > It's also very
On 04/01/18 03:13 PM, Jason Gunthorpe wrote:
On Thu, Jan 04, 2018 at 12:52:24PM -0700, Logan Gunthorpe wrote:
We tried things like this in an earlier iteration[1] which assumed the SG
was homogenous (all P2P or all regular memory). This required serious
ugliness to try and ensure SGs were in
On 04/01/18 12:22 PM, Jason Gunthorpe wrote:
This seems really clunky since we are going to want to do this same
logic all over the place.
I'd be much happier if dma_map_sg can tell the memory is P2P or not
from the scatterlist or dir arguments and not require the callers to
have this.
We
In order to use PCI P2P memory pci_p2pmem_[un]map_sg() functions must be
called to map the correct DMA address. To do this, we add a flags
variable and the RDMA_RW_CTX_FLAG_PCI_P2P flag. When the flag is
specified use the appropriate map function.
Signed-off-by: Logan Gunthorpe
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