Re: [Qemu-devel] [PATCH v1] s390x/pci: Warn when adding PCI devices without the 'zpci' feature

[David Hildenbrand <david@redhat.com>]

On 22.01.19 13:44, Cornelia Huck wrote:
> On Tue, 22 Jan 2019 10:41:43 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> We decided to always create the PCI host bridge, even if 'zpci' is not
>> enabled (due to migration compatibility). This however right now allows
>> to add zPCI/PCI devices to a VM although the guest will never actually see
>> them, confusing people that are using a simple CPU model that has no
>> 'zpci' enabled - "Why isn't this working" (David Hildenbrand)
>>
>> Let's check for 'zpci' and at least print a warning that this will not
>> work as expected. We could also bail out, however that might break
>> existing QEMU commandlines.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>  hw/s390x/s390-pci-bus.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index b86a8bdcd4..e7d4f49611 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -863,6 +863,11 @@ static void s390_pcihost_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
>>  {
>>      S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev);
>>  
>> +    if (!s390_has_feat(S390_FEAT_ZPCI)) {
>> +        warn_report("Adding PCI or zPCI devices without the 'zpci' CPU feature."
>> +                    " The guest will not be able to see/use these devices.");
>> +    }
>> +
>>      if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
>>          PCIDevice *pdev = PCI_DEVICE(dev);
>>  
> 
> That's hotplug only, isn't it? IIRC coldplugging already fails?
> 

No, applies also to coldplugging.

-- 

Thanks,

David / dhildenb