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Re: [PATCH 0/5] Fix recent PIC -> CPU interrupt wiring regressions

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH 0/5] Fix recent PIC -> CPU interrupt wiring regressions
Date: Tue, 7 Mar 2023 12:06:35 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.8.0

Hi Bernhard, Mark,

On 7/3/23 00:59, Mark Cave-Ayland wrote:
On 04/03/2023 11:40, Bernhard Beschow wrote:

A recent series [1] attempted to remove some PIC -> CPU interrupt indirections. This inadvertantly caused NULL qemu_irqs to be passed to the i8259 because the qemu_irqs aren't initialized at that time yet. This series provides a fix by
initializing the qemu_irq of the respective south bridges before they
are passed to i2859_init().

Furthermore -- as an optional extension -- this series also fixes some usability
issues in the API for creating multifunction PCI devices.

The series is structured as follows: The first three commits fix the
regressions, the last two fix the public API for creating multifunction PCI

[1] 20230302224058.43315-1-philmd@linaro.org/">https://lore.kernel.org/qemu-devel/20230302224058.43315-1-philmd@linaro.org/

Bernhard Beschow (5):
   hw/isa/vt82c686: Fix wiring of PIC -> CPU interrupt
   hw/alpha/dp264: Fix wiring of PIC -> CPU interrupt
   hw/ppc/prep: Fix wiring of PIC -> CPU interrupt
   hw/pci/pci: Remove multifunction parameter from
   hw/pci/pci: Remove multifunction parameter from

  include/hw/pci/pci.h |  4 +---
  hw/alpha/dp264.c     |  8 +++++---
  hw/i386/pc_piix.c    |  2 +-
  hw/i386/pc_q35.c     | 10 +++++-----
  hw/isa/vt82c686.c    |  3 ++-
  hw/mips/boston.c     |  3 +--
  hw/mips/fuloong2e.c  |  9 +++++----
  hw/mips/malta.c      |  2 +-
  hw/pci-host/sabre.c  |  6 ++----
  hw/pci/pci.c         | 18 ++++++++++++------
  hw/ppc/pegasos2.c    |  9 +++++----
  hw/ppc/prep.c        |  4 +++-
  hw/sparc64/sun4u.c   |  5 ++---
  13 files changed, 45 insertions(+), 38 deletions(-)

Thanks for doing this! The patches basically look good, the only minor niggle is that normally wiring of gpios is done *after* realize() for consistency because some qdev_init_gpio_*() functions may use a property to define the gpio array size.

Sorry this took me so long. The series LGTM too, but I wanted to well
understand the overall problem and run more tests.
Bernhard noticed that the bug is that we access the qdev gpios _before_
the device is realized.

The (undocumented) sysbus_connect_irq() API -- which calls
qdev_connect_gpio_out() -- is expected to be called _after_

Bernhard's fix is to call qdev_connect_gpio_out() _before_

Having said that it is a nice tidy-up, so I'd be okay with patches 1-3 if you added a small comment above the qdev_connect_gpio_out() lines pointing out that this is a temporary solution (hack?) until the 8259 device is converted to use gpios.

I agree, while this works, it is a "temporary solution" until we decide
and clarify the QDev/SysBus APIs w.r.t. IRQs.

However given that Phil wrote the patches I'd wait for him to decide whether he'd prefer a plain revert over the changes in this series before going ahead with a v2.

As discussed with Peter / Mark / David on IRC, a revert is wiser for
this release.

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