Re: [Qemu-devel] [Qemu-block] How to generate custom fw paths for IDE devices?

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

On 27/07/18 11:47, Paolo Bonzini wrote:

> On 27/07/2018 12:43, Mark Cave-Ayland wrote:
>> The issue here seems to be that according to "info qtree" there is
>> *always* an ide-cd device plugged into the location equivalent to that
>> of -cdrom, and so with the above command QEMU ends up adding a second
>> ide-cd device to the ide.1 bus which confuses OpenBIOS. Is this
>> deliberate behaviour?
> 
> Yes, the default CD-ROM is always placed as secondary/master.
> 
> If you use -device ide-cd the implicit CD-ROM should go away.  However,
> -drive alone doesn't have that effect (probably for backwards
> compatibility reasons, this predates me even though by only a few months).

I see, thanks for the detailed explanation. So in that case shouldn't 
the following work?

$ ./qemu-system-ppc -drive 
id=cd,file=MacOS921-macsbug.iso,if=ide,media=cdrom -device 
ide-cd,drive=cd,bootindex=0 -nographic -prom-env 'auto-boot?=false'

qemu-system-ppc: -device ide-cd,drive=cd,bootindex=0: Drive 'cd' is 
already in use because it has been automatically connected to another 
device (did you need 'if=none' in the drive options?)

 From what I can see you must have if=ide present so that the code will 
take into account that the machine block_default_type is set to IF_IDE 
and understand it's the existing internal IDE buses that need to be 
(re)used?

> Alternatively, you can use -nodefaults of course.

For the moment I'd like to come up with equivalents to the -hda and 
-cdrom options to allow users to switch to the new syntax, and of course 
this is all a pre-cursor to adding virtio support to OpenBIOS :)

It seems to me that -nodefaults is intended more for tools like libvirt 
that want to build up a machine from scratch, although again there is 
always the issue as to how to handle internal devices i.e. the 
difference between plugging a drive into an internal IDE interface vs. 
adding one into a spare PCI slot via -device and instead plugging the 
drive into that.


ATB,

Mark.