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Re: Problems with irq mapping in qemu v5.2


From: BALATON Zoltan
Subject: Re: Problems with irq mapping in qemu v5.2
Date: Wed, 23 Dec 2020 20:49:08 +0100 (CET)

On Wed, 23 Dec 2020, Philippe Mathieu-Daudé wrote:
On 12/22/20 5:16 PM, Guenter Roeck wrote:
Hi,

commit 459ca8bfa41 ("pci: Assert irqnum is between 0 and bus->nirqs in
pci_bus_change_irq_level") added sanity checks to the interrupt number passed
to pci_bus_change_irq_level(). That makes sense, given that bus->irq_count
is indexed and sized by the number of interrupts.

However, as it turns out, the interrupt number passed to this function
is the _mapped_ interrupt number. The result in assertion failures for various
emulations.

Examples (I don't know if there are others):

- ppc4xx_pci_map_irq() maps the interrupt number to "slot - 1". Obviously
  that isn't a good thing to do for slot 0, and indeed results in an
  assertion as soon as slot 0 is initialized (presumably that is the root
  bridge). Changing the mapping to "slot" doesn't help because valid slots
  are 0..4, and only four interrupts are allocated.
- pci_bonito_map_irq() changes the mapping all over the place. Whatever
  it does, it returns numbers starting with 32 for slots 5..12. With
  a total number of 32 interrupts, this again results in an assertion
  failure.

ppc4xx_pci_map_irq() is definitely buggy. I just don't know what the
correct mapping should be. slot  & 3, maybe ?

I don't really have a good solution for pci_bonito_map_irq(). It may not
matter much - I have not been able to boot fuloong_2e since qemu v4.0,
and afaics that is the only platform using it. Maybe it is just completely
broken ?

FWIW bisecting Fuloong2E starts failing here:

4ea98d317eb442c738f898f16cfdd47a18b7ca49 is the first bad commit
commit 4ea98d317eb442c738f898f16cfdd47a18b7ca49
Author: BALATON Zoltan <balaton@eik.bme.hu>
Date:   Fri Jan 25 14:52:12 2019 -0500

   ide/via: Implement and use native PCI IDE mode

   This device only implemented ISA compatibility mode and native PCI IDE
   mode was missing but no clients actually need ISA mode but to the
   contrary, they usually want to switch to and use device in native
   PCI IDE mode. Therefore implement native PCI mode and switch default
   to that.

   Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
   Message-id:
c323f08c59b9931310c5d92503d370f77ce3a557.1548160772.git.balaton@eik.bme.hu
   Signed-off-by: John Snow <jsnow@redhat.com>

hw/ide/via.c | 52 ++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 38 insertions(+), 14 deletions(-)

How did you test? What guest OS and version have you used?

Regards,
BALATON Zoltan

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