Re: Memory leak in via_isa_realize()

[BALATON Zoltan <balaton@eik.bme.hu>]

On Mon, 21 Mar 2022, Peter Maydell wrote:
> On Mon, 21 Mar 2022 at 10:31, Thomas Huth <thuth@redhat.com> wrote:
>> FYI, I'm seeing a memory leak in via_isa_realize() when building
>> QEMU with sanitizers enabled or when running QEMU through valgrind:
>> Same problem happens with qemu-system-ppc64 and the pegasos2 machine.
>>
>> No clue how to properly fix this... is it safe to free the pointer
>> at the end of the function?
>
> This is because the code is still using the old function
> qemu_allocate_irqs(), which is almost always going to involve
> it leaking memory. The fix is usually to rewrite the code to not use
> that function at all, i.e. to manage its irq/gpio lines differently.
> Probably the i8259 code should have a named GPIO output line
> rather than wanting to be passed a qemu_irq in an init function,
> and the via code should have an input GPIO line which it connects
> up to the i8259. It looks from a quick glance like the i8259 and
> its callers have perhaps not been completely QOMified.

Everything involving ISA emulation in QEMU is not completely QOMified and 
this has caused some problems before but I did not want to try to fix it 
both becuase it's too much unrelated work and because it's used by too 
many things that could break that I can't even test. So I'd rather 
somebody more comfortable with this would look at ISA QOMification.

> In this specific case, though, it seems like the only thing that
> the via_isa_request_i8259_irq() function does is pass the interrupt
> signal through to its own s->cpu_intr, so I think a relatively
> self-contained way to deal with the leak is to pass s->cpu_intr
> into i8259_init() and drop the isa_irq allocated irq and its
> associated helper function entirely. (There might be some subtlety
> I'm missing that means that wouldn't work, of course.)

I think I've tried to do that first and it did not work for some reason 
then I got this way from some other device model which works but I forgot 
the details. You can test it by booting MorphOS or Debian Linux 8.11 PPC 
on pegasos2 which support this machine or maybe I can have a look later 
this week if it's not urgent and try something but I don't mind if 
somebody comes up with a fix before that.

Regards,
BALATON Zoltan