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

[Bernhard Beschow]

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?

Thanks,
Bernhard

>
>> Second, pci_bus_set_route_irq_fn() is now also called in Xen mode.
>> 
>> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>
>Beside the leak which I think can happen only once, patch is fine:
>Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
>
>Thanks,
>