Re: [PATCH] PCI/P2PDMA: Root complex whitelist should not apply when an IOMMU is present

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Am 23.05.19 um 11:50 schrieb Christoph Hellwig:
> [CAUTION: External Email]
>
> On Thu, May 23, 2019 at 09:48:40AM +0000, Koenig, Christian wrote:
>> I don't adjust the address manually anywhere. I just call
>> dma_map_resource() and use the resulting DMA address to access the other
>> devices PCI BAR.
>>
>> At least on my test system (AMD CPU + AMD GPUs) this seems to work
>> totally fine. Currently trying to find time and an Intel box to test it
>> there as well.
> 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.

Ok, we certainly don't have a system which exercise this user case. 
Could ask around if we have an ARM SOC with that properties somewhere.

But asking the other way around: Where is the right place to start 
fixing all this? dma_map_resource()?

Christian.




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