Re: [PATCH v10 11/12] hw/pci: Convert rom_bar into OnOffAuto

[BALATON Zoltan]

On Wed, 3 Jul 2024, Michael S. Tsirkin wrote:
> On Wed, Jul 03, 2024 at 04:15:23AM +0200, BALATON Zoltan wrote:
> > On Tue, 2 Jul 2024, Michael S. Tsirkin wrote:
> > > On Thu, Jun 27, 2024 at 03:08:00PM +0900, Akihiko Odaki wrote:
> > > > rom_bar is tristate but was defined as uint32_t so convert it into
> > > > OnOffAuto.
> > > >
> > > > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> > >
> > > Commit log should explain why this is an improvement,
> > > not just what's done.
> > >
> > >
> > > > diff --git a/docs/igd-assign.txt b/docs/igd-assign.txt
> > > > index e17bb50789ad..35c6c8e28493 100644
> > > > --- a/docs/igd-assign.txt
> > > > +++ b/docs/igd-assign.txt
> > > > @@ -35,7 +35,7 @@ IGD has two different modes for assignment using vfio-pci:
> > > >        ISA/LPC bridge device (vfio-pci-igd-lpc-bridge) on the root bus at
> > > >        PCI address 1f.0.
> > > >      * The IGD device must have a VGA ROM, either provided via the romfile
> > > > -      option or loaded automatically through vfio (standard).  rombar=0
> > > > +      option or loaded automatically through vfio (standard).  rombar=off
> > > >        will disable legacy mode support.
> > > >      * Hotplug of the IGD device is not supported.
> > > >      * The IGD device must be a SandyBridge or newer model device.
> > >
> > > ...
> > >
> > > > diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
> > > > index 39dae72497e0..0e920ed0691a 100644
> > > > --- a/hw/vfio/pci-quirks.c
> > > > +++ b/hw/vfio/pci-quirks.c
> > > > @@ -33,7 +33,7 @@
> > > >   * execution as noticed with the BCM 57810 card for lack of a
> > > >   * more better way to handle such issues.
> > > >   * The  user can still override by specifying a romfile or
> > > > - * rombar=1.
> > > > + * rombar=on.
> > > >   * Please see https://bugs.launchpad.net/qemu/+bug/1284874
> > > >   * for an analysis of the 57810 card hang. When adding
> > > >   * a new vendor id/device id combination below, please also add
> > >
> > >
> > > So we are apparently breaking a bunch of users who followed
> > > documentation to the dot. Why is this a good idea?
> >
> > On/off is clearer than 1/0. But isn't 1/0 a synonym for on/off so previous
> > command lines would still work?
> >
> > Regards,
> > BALATON Zoltan
>
> I see nothing in code that would make it so:
>
>
> const QEnumLookup OnOffAuto_lookup = {
>    .array = (const char *const[]) {
>        [ON_OFF_AUTO_AUTO] = "auto",
>        [ON_OFF_AUTO_ON] = "on",
>        [ON_OFF_AUTO_OFF] = "off",
>    },
>    .size = ON_OFF_AUTO__MAX
> };
>
> I also tried with an existing property:
>
> $ ./qemu-system-x86_64 -device intel-hda,msi=0
> qemu-system-x86_64: -device intel-hda,msi=0: Parameter 'msi' does not accept 
> value '0'

Then it was probably bit properties that also accept 0/1, on/off, 
true/false. Maybe similar aliases could be added to on/off/auto?

In any case when I first saw rombar I thought it would set the BAR of the 
ROM so wondered why it's 1 and not 5 or 6 or an offset. So on/off is 
clearer in this case.

Regards,
BALATON Zoltan