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From: David Hildenbrand <david@redhat.com>
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Date: Wed, 23 Jan 2019 12:08:37 +0100
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Subject: Re: [Qemu-devel] [PATCH v3 1/2] s390x/pci: Introduce unplug
 requests and split unplug handler
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To: Cornelia Huck <cohuck@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-s390x@nongnu.org, Collin Walling <walling@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Richard Henderson <rth@twiddle.net>

On 23.01.19 12:03, Cornelia Huck wrote:
> On Mon, 21 Jan 2019 14:42:48 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> PCI on s390x is really weird and how it was modeled in QEMU might not have
>> been the right choice. Anyhow, right now it is the case that:
>> - Hotplugging a PCI device will silently create a zPCI device
>>   (if none is provided)
>> - Hotunplugging a zPCI device will unplug the PCI device (if any)
>> - Hotunplugging a PCI device will unplug also the zPCI device
>> As far as I can see, we can no longer change this behavior. But we
>> should fix it.
>>
>> Both device types are handled via a single hotplug handler call. This
>> is problematic for various reasons:
>> 1. Unplugging via the zPCI device allows to unplug PCI bridges as
>>    checks are not performed - bad.
> 
> Maybe I'm confused here, but how can a zPCI device couple with a bridge?
> 

I was confused, bridges don't attach to a zPCI device. So this remark is
invalid. Thanks!

-- 

Thanks,

David / dhildenb