Am 23.05.19 um 17:59 schrieb Christoph Hellwig:
> [CAUTION: External Email]
>
> On Thu, May 23, 2019 at 09:53:53AM -0600, Logan Gunthorpe wrote:
>>> The problem shows up if pci_bus_address() returns a different address
>>> than pci_resource_start(), should be easy to check if that happens.
>>> IIRC it is something mostly seen on embedded SOCs.
>>>
>> I think it's a bit more complicated then that: If you're calling
>> dma_map_resource() to program the IOMMU then I'm pretty sure you'd want
>> to use the pci_resource_start() address as the phys_addr_t. If you're
>> bypassing the root complex (like the current p2pdma code enforces), then
>> you'd simply use a pci_bus_address() directly as the dma_addr and would
>> not program the IOMMU at all seeing it's not involved (which is what is
>> currently done).
> True. What we need is:
>
> if (both device are behind the same root port (using a switch)) {
> use the current direct map + offset code
> } else {
> call ->map_resource()
> }
Sounds sane to me as well.
But since I don't have a struct pages backing my PCI BAR I won't be able
to use pci_p2pdma_map_sg.
How should we work around that?
Regards,
Christian.
