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

[Jason Andryuk]

On Mon, Apr 3, 2023 at 5:33 AM Anthony PERARD <anthony.perard@citrix.com> 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@citrix.com>:
> > >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?

Regards,
Jason