# RE: \[PATCH\] PCI: hv: Detect and fix Hyper-V PCI domain number collision

- From: Dexuan Cui \<decui@microsoft.com\>
- Date: 2019-05-22 05:14:50 
- List: linux-hyperv
- Page: https://ratatoskr.run/linux-hyperv/2019/05/5603776
- Thread: https://ratatoskr.run/linux-hyperv/2019/05/5603776/t.md

```text
> From: Stephen Hemminger <redacted> 
> Sent: Tuesday, May 21, 2019 9:40 PM
>
> Thanks for working this out with the host team.
> Now if we could just get some persistent slot information it would make udev in systemd happy.

The slot info comes from the serial number "hpdev->desc.ser", which may not guarantee
uniqueness: "...Hyper-V doesn't provide unique serial numbers": see the changelog of the below
commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=29927dfb7f69bcf2ae7fd1cda10997e646a5189c

And we can pass through multiple devices to a VM in any order (i.e. hot add/remove), so IMO
the "slot" info is not unique and persistent.

Thanks,
-- Dexuan
```