On Fri, Nov 29, 2019 at 06:59:48AM +0000, bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=205701 > ... > > Using Intel Xeon computer with linux kernel 4.18.0 centos8. > Trying to access RAM (with DMA) using FPGA fails in this computer. > > 1. I tried to add intel_iommu=off - it did not help. > > 2. Installing windows on same PC - FPGA can access RAM using DMA without > issues. > > 3. using another PC (Intel Duo) with same linux and OS - FPGA access works. > > FPGA access the RAM using a physical address provided by a kernel module which > allocates physical continuous memory in PC. (the module works perfectly with > Intel Duo on exactly same OS and kernel). Hi, thanks for the report! Can you please attach the complete dmesg and "sudo lspci -vv" output for the working and non-working v4.18 kernels to the bugzilla? Then please try to reproduce the problem on the current v5.4 kernel and attach the v5.4 dmesg log. If v5.4 fails, we'll have to debug it. If v5.4 works, figure out what fixed it (by comparing dmesg logs or by bisection) and backport it to v4.18. Bjorn
