Re: [PATCH v2 06.5/18] hw/ide/piix: Allow using PIIX3-IDE as standalone PCI function

[Gerd Hoffmann]

On Mon, Feb 20, 2023 at 09:00:44AM +0100, Philippe Mathieu-Daudé wrote:
> In order to allow Frankenstein uses such plugging a PIIX3
> IDE function on a ICH9 chipset (which already exposes AHCI
> ports...) as:
> 
>   $ qemu-system-x86_64 -M q35 -device piix3-ide
> 
> add a kludge to automatically wires the IDE IRQs on an ISA
> bus exposed by a PCI-to-ISA bridge (usually function #0).
> Restrict this kludge to the PIIX3.

Well.  On physical hardware you have a config switch in the bios
setup which turns off sata and enables ide instead (i.e. the
chipset implements both and can be configured to expose the one
or the other).

If we want support ide for q35 we should IMHO do something simliar
instead of making piix-ide user-pluggable.  We already have -machine
q35,sata={on,off}.  We could extend that somehow, by adding
ide={on,off}, or by using storage={sata,ide,off} instead.

This has been discussed now and then in the past and the usual
conclusion was that there is little reason to implement that given
that you can just use the 'pc' machine type.  For guests that old
that they can't handle sata storage this is usually the better fit
anyway ...

take care,
  Gerd