On Wed, 5 Dec 2018 11:05:58 +0000 Gareth Bradshaw <gar...@vectra.ai> wrote:
> Hi, > > I'm developing a DPDK application for Hyper-V and would like to use Kernel > v4.20 as it fixes a crash in previous kernels (per this pull > request<https://github.com/torvalds/linux/commit/cdfa835c6e5e87d145f9f632b58843de97509f2b>) > but multi-queue support seems to have broken in that kernel. It works in > kernels 4.17, 4.18 and 4.19. > > Using testpmd with parameters "--forward-mode=txonly --nb-cores=3 --txq=3 > --rxq=3" I get the following error "vmbus_uio_get_subchan(): invalid > subchannel id 0". > > Tracing the code a bit I find that it's trying to read > /sys/bus/devices/<devid>/channels/21/subchannel_id but when I try to cat the > same file I get the error "Invalid argument". I've compared to previous > kernel versions and see the following differences: > > * When the VM boots, the device is bound to the kernel driver and there > are 4 channels on both kernel versions. It's a 4 core VM. > * When I bind the device to uio_hv_generic, kernel v.19.5 (and previous) > has a single channel and it has a valid subchannel_id. On kernel 4.20 the 4 > channel folders remain but they are all invalid. > * When I start testpmd with 3 queues, on kernel v4.19.5 two additional > channels are created, they're valid and testpmd works as expected. On kernel > 4.20 the 4 invalid channels remain invalid and testpmd gives the error I > mentioned. > > Any help getting this working would be greatly appreciated. > > Thanks > Gareth > > > > > > There is a race that shows up in sub channel initialization, it is being worked on the development mailing list. No resolution yet.
