Re: [PATCH 0/3] Resolve vt82c686 and piix4 qemu_irq memory leaks

[Bernhard Beschow]

Am 20. Juli 2024 18:38:42 UTC schrieb "Michael S. Tsirkin" <mst@redhat.com>:
>On Thu, Jul 04, 2024 at 10:58:51PM +0200, Bernhard Beschow wrote:
>> This series first turns vt82c686's "INTR" pin into a named GPIO for better
>> comprehensibility. It then continues fixing qemu_irq memory leaks in vt82c686
>> and piix4 by connecting out IRQs of the south bridges before they get 
>> realized.
>> This approach is already used in the pc machines after it had been discussed 
>> at
>> KVM forum `23.
>> 
>> Observe that out IRQs are callbacks such as an INTR IRQ handler in a CPU 
>> which a
>> south bridge wants to trigger. If, as an implementation detail, the south 
>> bridge
>> wants to pass this callback to a child device, such as the PIC, then this
>> callback must be known to the south bridge before it gets realized. Otherwise
>> board code had to wire the PIC device itself, breaking encapsulation. This 
>> means
>> that qdev_connect_gpio_out*() has to be called before realize() which this
>> series implements. Another way to look at it is that callbacks apparently are
>> resouces such as memory regions which are also populated before realize().
>> 
>> Please check if above paragraph makes sense.
>> 
>> Best regards,
>> Bernhard
>
>
>Bernhard, do you intend to resolve Zoltan's comments on this
>patchset?

Hi Michael,

I was hoping for some more comments on the last two commits. These resolve 
various issues in one go, some of which have been addressed in the past. Since 
this is apparently a new style to handle out-GPIOs, I'd like to get an OK from 
the community.

As Zoltan writes the ideal solution might be to qdev'ify the PIC. This is a 
bigger task which is more than I intended to do in this series.

Best regards,
Bernhard

>
>Thanks!
>
>
>> See also:
>> * 
>> https://lore.kernel.org/qemu-devel/0FFB5FD2-08CE-4CEC-9001-E7AC24407A44@gmail.
>> com/
>> * "Remove intermediate IRQ forwarder" patches in
>> https://lore.kernel.org/qemu-devel/20230210163744.32182-1-philmd@linaro.org/
>> 
>> Testing done:
>> * Boot amigaone machine into Linux
>> * Boot pegasos2 machine into MorphOS
>> * Start fuloong2e machine and check that it doesn't abort
>> * Boot malta machine with https://people.debian.org/~gio/dqib/
>> 
>> Bernhard Beschow (3):
>>   hw/isa/vt82c686: Turn "intr" irq into a named gpio
>>   hw/isa/vt82c686: Resolve intermediate IRQ forwarder
>>   hw/isa/piix: Resolve intermediate IRQ forwarder
>> 
>>  hw/isa/piix.c       | 13 ++-----------
>>  hw/isa/vt82c686.c   | 12 ++----------
>>  hw/mips/fuloong2e.c |  2 +-
>>  hw/mips/malta.c     |  4 +---
>>  hw/ppc/amigaone.c   |  8 ++++----
>>  hw/ppc/pegasos2.c   |  4 ++--
>>  6 files changed, 12 insertions(+), 31 deletions(-)
>> 
>> -- 
>> 2.45.2
>> 
>