On 2018å¹´01æ??24æ?¥ 18:52, Christian König wrote: > Am 24.01.2018 um 11:32 schrieb Chunming Zhou: >> On 2018å¹´01æ??24æ?¥ 17:49, Christian König wrote: >>> [SNIP] >>> Nope, as I wrote that won't work. You must improve the detection if >>> we need coherent or not coherent allocation. >> But how to differentiate coherent or not coherent allocation? check >> if max io address of system memory under 40bits pcie address space? >> Do you know how to get the max io address of system memory? > > Well that is a good question, which nobody had an answer for so far > (and a couple of people already looked into it). > > We could start by checking if max_pfn is <= the 40bits limit or if > IOMMU is enabled instead of SWIOTLB. How to get max_pfn? btw, seems only amdgpu and radeon driver use dma path. Regards, David Zhou > > Regards, > Christian.
