Re: [Qemu-devel] virtio-blk-pci: how to tell if it is CD or HDD?

[Paolo Bonzini <pbonzini@redhat.com>]

Il 17/10/2013 14:38, Alexey Kardashevskiy ha scritto:
> qdev_get_fw_dev_path:
> /spapr-vio-bridge/spapr-vscsi/channel@0/disk@3,2 suffix=(null)
> /spapr-vio-bridge/spapr-vscsi/channel@0/disk@3,1 suffix=(null)

You need to implement qdev_fw_get_path to change

 spapr-vio-bridge -> vdevice
 spapr-vscsi -> v-scsi@REG

> /pci@800000020000000/ethernet@1 suffix=/ethernet-phy@0

The extra suffix is not a problem since you can parse a prefix successfully.

> /pci@800000020000000/scsi@0/channel@0/disk@3,2 suffix=(null)
> /pci@800000020000000/scsi@0/channel@0/disk@3,1 suffix=(null)

I guess this is virtio-scsi.

> SLOF:
> 0 > devalias
> cdrom123 : /pci@800000020000000/scsi@0/disk@103000100000000
> cdrom12 : /pci@800000020000000/scsi@0/disk@103000200000000
> hvterm : /vdevice/vty@71000100
> net : /pci@800000020000000/ethernet@1
> scsi : /vdevice/v-scsi@71000001
> cdrom1 : /vdevice/v-scsi@71000001/disk@8301000000000000
> cdrom : /vdevice/v-scsi@71000001/disk@8302000000000000
> nvram : /vdevice/nvram@71000000 ok
> 
> 
> In ideal world I would want to get in QEMU what SLOF can understand and
> pass this to SLOF. But QEMU APIs return something which cannot be converted
> straight away.
> 
> Or I could simply put bootindex to the device tree nodes (as
> "qemu,bootindex") but in this case "wildcard" nodes support fails as there
> is just a single node "/vdevice/v-scsi@71000001/disk" in the device tree
> for all LUNs. And we definitely do not want to create nodes for all disk
> devices.
> 
> Or I can implement a "smart" converter from QEMU strings to OF pathnames.
> 
> Or I can implement third set of callbacks, something like qdev_OF_dev_path().
> 
> Or not support "bootindex" at all.
> 
> All possibilities suck but which one sucks less? :) Thanks!

In general, try to make QEMU produce SLOF APIs by modifying the devices
that instantiate the buses.

On top of this, fix the remaining QEMU->OF differences using a callback
in QEMUMachine.  This callback would be called by
qdev_get_fw_dev_path_helper and, if it returns something non-NULL, the
result would be used instead of calling bus_get_fw_dev_path.

> btw what format does qdev_get_fw_dev_path() use? This is not OF1275 so what
> is it?

It is based on open-firmware.  For SCSI however openfirmware had
"disk@TARGET,LUN" but that does not include the channel.

Paolo