On Tue, Dec 06, 2022 at 09:44:08AM -0400, Jason Gunthorpe wrote: > On Tue, Dec 06, 2022 at 07:19:40AM +0100, Christoph Hellwig wrote: > > On Tue, Dec 06, 2022 at 01:58:12PM +0800, Lei Rao wrote: > > > The new function nvme_submit_vf_cmd() helps the host VF driver to issue > > > VF admin commands. It's helpful in some cases that the host NVMe driver > > > does not control VF's admin queue. For example, in the virtualization > > > device pass-through case, the VF controller's admin queue is governed > > > by the Guest NVMe driver. Host VF driver relies on PF device's admin > > > queue to control VF devices like vendor-specific live migration commands. > > > > WTF are you even smoking when you think this would be acceptable? > > Not speaking to NVMe - but this driver is clearly copying mlx5's live > migration driver, almost completely - including this basic function. > > So, to explain why mlx5 works this way.. > > The VFIO approach is to fully assign an entire VF to the guest OS. The > entire VF assignment means every MMIO register *and all the DMA* of > the VF is owned by the guest operating system. > > mlx5 needs to transfer hundreds of megabytes to gigabytes of in-device > state to perform a migration. For storage, though, you can't just transfer the controller state. You have to transfer all the namespace user data, too. So potentially many terabytes?
