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

[David Hildenbrand]

On 31.01.19 21:26, Collin Walling wrote:
> 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. :)

Yes, that's how it should work :)

> 
> 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.

Yes, it's pretty much to the guest like this device never existed.

Thanks!

> 
> Reviewed-by: Collin Walling <address@hidden>
> 


-- 

Thanks,

David / dhildenb