On 11/5/18 6:50 AM, David Hildenbrand wrote: > On 05.11.18 12:40, Christian Borntraeger wrote: >> >> >> On 11/05/2018 12:37 PM, David Hildenbrand wrote: >>> On 05.11.18 12:21, Cornelia Huck wrote: >>>> On Mon, 5 Nov 2018 12:03:11 +0100 >>>> David Hildenbrand <da...@redhat.com> wrote: >>>> >>>>> We directly have it in our hands. >>>>> >>>>> Signed-off-by: David Hildenbrand <da...@redhat.com> >>>>> --- >>>>> hw/s390x/s390-pci-bus.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c >>>>> index 1eaae3aca6..68660eac74 100644 >>>>> --- a/hw/s390x/s390-pci-bus.c >>>>> +++ b/hw/s390x/s390-pci-bus.c >>>>> @@ -814,9 +814,9 @@ static bool s390_pci_alloc_idx(S390pciState *s, >>>>> S390PCIBusDevice *pbdev) >>>>> static void s390_pcihost_plug(HotplugHandler *hotplug_dev, DeviceState >>>>> *dev, >>>>> Error **errp) >>>>> { >>>>> + S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev); >>>>> PCIDevice *pdev = NULL; >>>>> S390PCIBusDevice *pbdev = NULL; >>>>> - S390pciState *s = s390_get_phb(); >>>>> >>>>> if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) { >>>>> BusState *bus; >>>>> @@ -924,11 +924,11 @@ static void s390_pcihost_timer_cb(void *opaque) >>>>> static void s390_pcihost_unplug(HotplugHandler *hotplug_dev, DeviceState >>>>> *dev, >>>>> Error **errp) >>>>> { >>>>> + S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev); >>>>> PCIDevice *pci_dev = NULL; >>>>> PCIBus *bus; >>>>> int32_t devfn; >>>>> S390PCIBusDevice *pbdev = NULL; >>>>> - S390pciState *s = s390_get_phb(); >>>>> >>>>> if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) { >>>>> error_setg(errp, "PCI bridge hot unplug currently not >>>>> supported"); >>>> >>>> Not sure whether that is an improvement (s390_get_phb() caches the >>>> value, and is called from multiple other places as well.) >>>> >>> >>> Looking up a variable that is directly passed as an argument doesn't >>> look clean to me. >> >> I think there was a reason for this caching, namely that qom resolution can >> be quite expensive. For the hotplug case this obviously does not matter but >> for all the other cases it might. So do we really want to have different >> places use different methods? >> > > Caching resolution is fine (as that is expensive), caching a downcast is > as far as I remember not necessary. Especially, as you said, for hotplug > handlers. > > Anyhow, if there are strong feelings to this change, I can drop this > patch. There are certainly more important things to do in zPCI hotplug code. > >
Truthfully, I'm not in favor of one over the other. As long as the device handlers are consistent, I think either is fine. However, it would be nice if at some point during plug we cache the PHB somewhere. That would be some sort of best-of-both-worlds approach. -- Respectfully, - Collin Walling