Re: VFIO/vfio-user: specify NVMe namespace to boot from

[Stefan Hajnoczi]

On Mon, Jul 12, 2021 at 01:24:07PM +0000, Thanos Makatos wrote:
> We're working on implementing a virtual NVMe controller based on SPDK and a 
> multiprocess-qemu branch that uses the vfio-user. We're facing a problem 
> where the existing API doesn't allow us to tell QEMU from which NVMe 
> namespace we'd like SeaBIOS to boot from.
> 
> How can we solve this problem? Can we add a parameter to the '-boot' option, 
> e.g. '-boot path=/devices/pciblah/...@namespace0'? AFAIK VFIO should have the 
> same problem. 
> 
> The corresponding SeaBIOS patch can be found in 
> https://mail.coreboot.org/hyperkitty/list/seabios@seabios.org/thread/2Q7NPH7TJNHK6JGPHQL7755HILO23ISN/

Hi,
I have CCed Gerd Hoffmann on a hunch that he may have ideas.

Yes, I think the path needs to include the Namespace ID similar to how
SCSI boot paths include the target/channel/LUN.

When the SeaBIOS NVMe driver probes the controller is should discover
the available Namespaces and set up individual drives for each
Namespace. That would be analogous to virtio_scsi_add_lun().

Stefan

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