> 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/seab...@seabios.org/thread/2Q7 > NPH7TJNHK6JGPHQL7755HILO23ISN/ > > 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.
Just to make sure I've explained the problem correctly, what we need to fix is not specific to NVMe: we want to be able to boot from any PCI device, so we'd need something like '-boot /devices/pciblah'. Specifically, for NVMe we might want to specify the namespace (as we can't necessarily assume that the first one must be used), therefore we'd have to add the '/namespace0' bit. For other kinds of PCI devices, we'd have to append something different. Would such a change be acceptable? > > 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(). Setting up an individual drive can easily exhaust SeaBIOS's limited memory, so it's better to either probe the specified namespace or probe the first active one. I've sent a patch here: https://mail.coreboot.org/hyperkitty/list/seab...@seabios.org/message/TKKUCH5PYZPXZG3NA2F5SALUFUVUYDZG/
