Am 19.06.19 um 01:50 schrieb Logan Gunthorpe: > > On 2019-06-18 2:51 p.m., Logan Gunthorpe wrote: >> On 2019-06-18 2:40 p.m., Bjorn Helgaas wrote: >>> On Wed, May 22, 2019 at 02:12:52PM -0600, Logan Gunthorpe wrote: >>>> Presently, there is no path to DMA map P2PDMA memory, so if a TLP >>>> targeting this memory hits the root complex and an IOMMU is present, >>>> the IOMMU will reject the transaction, even if the RC would support >>>> P2PDMA. >>>> >>>> So until the kernel knows to map these DMA addresses in the IOMMU, >>>> we should not enable the whitelist when an IOMMU is present. >>>> >>>> While we are at it, remove the comment mentioning future work >>>> to add a white list. >>> There was a lot of discussion about this. Did everybody come to a >>> consensus about what should be done? Can you post a patch with >>> reviewed-by if appropriate? >> I think we have consensus that it's broken and needs to be fixed for the >> short term. Preferably before 5.3. Yeah, completely agree. >> I'm not sure we have consensus on the >> proper fix. >> >> The two easy things I can see to do is to either revert it or add the >> iommu_is_present() check that I did in the above patch. >> >> @Christian, which do you prefer? I think I'd prefer the >> iommu_is_present() route as it maintains the information about >> white-listed devices and is easier to change once we have the correct >> solution. Your original iommu_is_prevent() patch sound like the best option so far. If that hasn't changed feel free to add a Reviewed-by: Christian König <christian.koenig@xxxxxxx> to that one. >> I can send a patch tomorrow one way or another. > Also, looks like one of my clients has an interest in seeing work like > this happen. So I'll be writing some patches in the next couple weeks to > do this properly. I'll try to send them to the lists early next cycle. Oh, nice. I was hoping to get my use case into 5.4 or 5.5, but we are still stuck with some of the DMA-buf related pieces. Regards, Christian. > > Logan
