Re: [PATCH v3 2/6] hw/isa/piix3: Reuse piix3_realize() in piix3_xen_realize()

[Bernhard Beschow <shentey@xxxxxxxxx>]

Am 3. April 2023 12:27:14 UTC schrieb Jason Andryuk <jandryuk@xxxxxxxxx>:
>On Mon, Apr 3, 2023 at 5:33 AM Anthony PERARD <anthony.perard@xxxxxxxxxx> 
>wrote:
>>
>> On Sat, Apr 01, 2023 at 10:36:45PM +0000, Bernhard Beschow wrote:
>> >
>> >
>> > Am 30. März 2023 13:00:25 UTC schrieb Anthony PERARD 
>> > <anthony.perard@xxxxxxxxxx>:
>> > >On Sun, Mar 12, 2023 at 01:02:17PM +0100, Bernhard Beschow wrote:
>> > >> This is a preparational patch for the next one to make the following
>> > >> more obvious:
>> > >>
>> > >> First, pci_bus_irqs() is now called twice in case of Xen where the
>> > >> second call overrides the pci_set_irq_fn with the Xen variant.
>> > >
>> > >pci_bus_irqs() does allocates pci_bus->irq_count, so the second call in
>> > >piix3_xen_realize() will leak `pci_bus->irq_count`. Could you look if
>> > >pci_bus_irqs_cleanup() can be called before the second pci_bus_irqs()
>> > >call, or maybe some other way to avoid the leak?
>> >
>> > Thanks for catching this! I'll post a v4.
>> >
>> > I think the most fool-proof way to fix this is to free irq_count just 
>> > before the assignment. pci_bus_irqs_cleanup() would then have to NULL the 
>> > attribute such that pci_bus_irqs() can be called afterwards.
>> >
>> > BTW: I tried running qemu-system-x86_64 with PIIX4 rather than PIIX3 as 
>> > Xen guest with my pc-piix4 branch without success. This branch essentially 
>> > just provides slightly different PCI IDs for PIIX. Does xl or something 
>> > else in Xen check these? If not then this means I'm still missing 
>> > something. Under KVM this branch works just fine. Any idea?
>>
>> Maybe the ACPI tables provided by libxl needs to be updated.
>> Or maybe something in the firmware (SeaBIOS or OVMF/OvmfXen) check the
>> id (I know that the PCI id of the root bus is checked, but I don't know
>> if that's the one that's been changed).
>
>Xen also has hvmloader, which runs before SeaBIOS/OVMF.  Looking at
>tools/firmware/hvmloader/pci.c, it has
>        ASSERT((devfn != PCI_ISA_DEVFN) ||
>               ((vendor_id == 0x8086) && (device_id == 0x7000)));
>
>From QEMU, it looks like 0x7000 is PCI_DEVICE_ID_INTEL_82371SB_0, but
>PIIX4 uses 0x7110 (PCI_DEVICE_ID_INTEL_82371AB_0).  Maybe try removing
>that check?

I was finally able to build Xen successfully (without my distribution providing 
too recent dependencies that prevent compilation). With 0x7110 added in the 
line above I could indeed run a Xen guest with PIIX4. Yay!

Now I just need to respin my PIIX consolidation series...

Best regards,
Bernhard

>
>Regards,
>Jason