Re: [Qemu-devel] [PATCH v2 6/6] s390x/pci: Unplug remaining requested devices on pcihost reset

[Collin Walling]

On 1/30/19 10:57 AM, David Hildenbrand wrote:
> When resetting the guest we should unplug and remove all devices that
> are still pending.
>
> With this patch, the requested device will be unpluged on reboot
> (S390_RESET_EXTERNAL and S390_RESET_REIPL, which reset the pcihost bridge
> via qemu_devices_reset()).
>
> This approach is similar to what's done for acpi PCI hotplug in
> acpi_pcihp_reset() -> acpi_pcihp_update() ->
> acpi_pcihp_update_hotplug_bus() -> acpi_pcihp_eject_slot().
>
> s390_pci_generate_plug_event()'s will still be generated, I guess this
> is not an issue. The same thing would happen right now when unplugging
> a device just before starting the guest.
>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>   hw/s390x/s390-pci-bus.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>
> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> index 867801ccf9..b9b0f44087 100644
> --- a/hw/s390x/s390-pci-bus.c
> +++ b/hw/s390x/s390-pci-bus.c
> @@ -1092,6 +1092,21 @@ static void s390_pcihost_reset(DeviceState *dev)
>   {
>       S390pciState *s = S390_PCI_HOST_BRIDGE(dev);
>       PCIBus *bus = s->parent_obj.bus;
> +    S390PCIBusDevice *pbdev, *next;
> +
> +    /* Process all pending unplug requests */
> +    QTAILQ_FOREACH_SAFE(pbdev, &s->zpci_devs, link, next) {
> +        if (pbdev->unplug_requested) {
> +            if (pbdev->summary_ind) {
> +                pci_dereg_irqs(pbdev);
> +            }
> +            if (pbdev->iommu->enabled) {
> +                pci_dereg_ioat(pbdev->iommu);
> +            }
> +            pbdev->state = ZPCI_FS_STANDBY;
> +            s390_pci_perform_unplug(pbdev);
> +        }
> +    }
>   
>       /*
>        * When resetting a PCI bridge, the assigned numbers are set to 0. So

Just "talking out loud" to reaffirm my understanding:

The ..._unplug_request function will have already generated the
deconfigure unplug event, and the unplug_requested flag will be set.
Makes sense -- easy to follow. :)

The callback that this code is essentially replacing used to generate a
CONFIGURED_TO_STBRES plug event, but as I recall from a previous
conversation regarding PCI states, we can skip this event because we're
removing the device from the guest during a reset here (there are a few
reasons why we'd do this, but no sense in listing them here). Also makes
sense to me.

Reviewed-by: Collin Walling <address@hidden>