[+cc Alex, Cornelia, kvm, lkml (from "get_maintainer.pl drivers/vfio") and rewrapped for plain-text readability] On Thu, Aug 04, 2022 at 09:47:36AM +0000, Arinzon, David wrote: > Hi, > > There's currently no mechanism for vfio that exposes WC-related > operations (check if memory is WC capable, ask to WC memory) to user > space module entities, such as DPDK, for example. > > This topic has been previously discussed in [1], [2] and [3], but > there was no follow-up. > > This capability is very useful for DPDK, specifically to the DPDK > ENA driver that uses vfio-pci, which requires memory to be WC on the > TX path. Without WC, higher CPU utilization and performance > degradation are observed. > > In the above mentioned discussions, three options were suggested: > sysfs, ioctl, mmap extension (extra attributes). > > Was there any progress on this area? Is there someone who's looking > into this? > > We're leaning towards the ioctl option, if there are no objections, > we'd come up with an RFC. > [1]: https://patchwork.kernel.org/project/kvm/patch/20171009025000.39435-1-aik@xxxxxxxxx/ > [2]: https://lore.kernel.org/linux-pci/2b539df4c9ec703458e46da2fc879ee3b310b31c.camel@xxxxxxxxxxxxxxxxxxx/ > [3]: https://lore.kernel.org/lkml/20210429162906.32742-2-sdonthineni@xxxxxxxxxx/ > > Thanks, > David
