Re: [Qemu-devel] [PATCH v3 2/5] virtio_net: Add support for "Data Path Switching" during Live Migration.

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jan 07, 2019 at 05:29:41PM -0500, Venu Busireddy wrote:
> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
> index 80d42e1..2a3ffd3 100644
> --- a/hw/acpi/pcihp.c
> +++ b/hw/acpi/pcihp.c
> @@ -176,6 +176,25 @@ static void acpi_pcihp_eject_slot(AcpiPciHpState *s, unsigned bsel, unsigned slo
>      }
>  }
>  
> +static void acpi_pcihp_cleanup_failover_primary(AcpiPciHpState *s, int bsel)
> +{
> +    BusChild *kid, *next;
> +    PCIBus *bus = acpi_pcihp_find_hotplug_bus(s, bsel);
> +
> +    if (!bus) {
> +        return;
> +    }
> +    QTAILQ_FOREACH_SAFE(kid, &bus->qbus.children, sibling, next) {
> +        DeviceState *qdev = kid->child;
> +        PCIDevice *pdev = PCI_DEVICE(qdev);
> +        int slot = PCI_SLOT(pdev->devfn);
> +
> +        if (pdev->failover_primary) {
> +            s->acpi_pcihp_pci_status[bsel].down |= (1U << slot);
> +        }
> +    }
> +}
> +
>  static void acpi_pcihp_update_hotplug_bus(AcpiPciHpState *s, int bsel)
>  {
>      BusChild *kid, *next;

So the result here will be that device will be deleted completely,
and will not reappear after guest reboot.
I don't think this is what we wanted.
I think we wanted a special state that will hide device from guest until
guest acks the failover bit.


> @@ -207,6 +226,14 @@ static void acpi_pcihp_update(AcpiPciHpState *s)
>      int i;
>  
>      for (i = 0; i < ACPI_PCIHP_MAX_HOTPLUG_BUS; ++i) {
> +        /*
> +         * Set the acpi_pcihp_pci_status[].down bits of all the
> +         * failover_primary devices so that the devices are ejected
> +         * from the guest. We can't use the qdev_unplug() as well as the
> +         * hotplug_handler to unplug the devices, because the guest may
> +         * not be in a state to cooperate.
> +         */
> +        acpi_pcihp_cleanup_failover_primary(s, i);
>          acpi_pcihp_update_hotplug_bus(s, i);
>      }
>  }

I really don't want acpi to know anything about failover.

All that needs to happen is sending a device delete request
to guest. Should work with any hotplug removal:
pci standard,acpi, etc.


-- 
MST