Re: [PATCH v3 00/18] hw/ide: Untangle ISA/PCI abuses of ide_init_ioport()

[Mark Cave-Ayland]

On 03/03/2023 06:58, David Woodhouse wrote:

> On 2 March 2023 22:40:40 GMT, "Philippe Mathieu-Daudé" <philmd@linaro.org> 
> wrote:
> > Since v2: rebased
> >
> > I'm posting this series as it to not block Bernhard's PIIX
> > cleanup work. I don't have code change planned, but eventually
> > reword / improve commit descriptions.
> >
> > Tested commit after commit to be sure it is bisectable. Sadly
> > this was before Zoltan & Thomas report a problem with commit
> > bb98e0f59c ("hw/isa/vt82c686: Remove intermediate IRQ forwarder").
>
> However much I stare at the partial revert which fixes it, I just cannot 
> believe that the change could make any difference at all. There's got to be 
> something weird going on there.
>
> I was going to ask if the level mode for the PIT made any difference, but this 
> is the output IRQ from the PIT to the CPU itself so I don't see how it would.
>
> Would like to see a report with tracing from pic_update_irq, the CPU interrupt 
> "handler" and the intermediate IRQ handler. With the intermediate present and 
> without it. To compare the two.

I suspect it's related to the removal of the allocation of the qemu_irq: qdev gpios 
work by adding a child IRQ object to the device, so it could be possible that 
something in the gpio internals isn't being updated correctly when the value is 
overwritten directly.

Is the problem picked up when running a binary built with --enable-sanitizers? That's 
normally quite good at detecting this kind of issue.


ATB,

Mark.