On Thu, Mar 25, 2021 at 01:20:21PM -0500, Bjorn Helgaas wrote: > On Thu, Mar 25, 2021 at 02:36:46PM -0300, Jason Gunthorpe wrote: > > On Thu, Mar 25, 2021 at 12:21:44PM -0500, Bjorn Helgaas wrote: > > > > > NVMe and mlx5 have basically identical functionality in this respect. > > > Other devices and vendors will likely implement similar functionality. > > > It would be ideal if we had an interface generic enough to support > > > them all. > > > > > > Is the mlx5 interface proposed here sufficient to support the NVMe > > > model? I think it's close, but not quite, because the the NVMe > > > "offline" state isn't explicitly visible in the mlx5 model. > > > > I thought Keith basically said "offline" wasn't really useful as a > > distinct idea. It is an artifact of nvme being a standards body > > divorced from the operating system. > > > > In linux offline and no driver attached are the same thing, you'd > > never want an API to make a nvme device with a driver attached offline > > because it would break the driver. > > I think the sticky part is that Linux driver attach is not visible to > the hardware device, while the NVMe "offline" state *is*. An NVMe PF > can only assign resources to a VF when the VF is offline, and the VF > is only usable when it is online. > > For NVMe, software must ask the PF to make those online/offline > transitions via Secondary Controller Offline and Secondary Controller > Online commands [1]. How would this be integrated into this sysfs > interface? Either the NVMe PF driver tracks the driver attach state using a bus notifier and mirrors it to the offline state, or it simply offline/onlines as part of the sequence to program the MSI change. I don't see why we need any additional modeling of this behavior. What would be the point of onlining a device without a driver? Jason
