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

- From: Bjorn Helgaas \<helgaas@kernel.org\>
- Date: 2019-08-06 18:55:35 
- List: linux-hyperv
- Page: https://ratatoskr.run/linux-hyperv/2019/08/5679857
- Thread: https://ratatoskr.run/linux-hyperv/2019/08/5677021/t.md

```text
On Mon, Aug 05, 2019 at 02:36:57PM -0400, Sasha Levin wrote:
> On Fri, Aug 02, 2019 at 06:52:56PM +0000, Haiyang Zhang wrote:
> > Due to Azure host agent settings, the device instance ID's bytes 8 and 9
> > are no longer unique. This causes some of the PCI devices not showing up
> > in VMs with multiple passthrough devices, such as GPUs. So, as recommended
> > by Azure host team, we now use the bytes 4 and 5 which usually provide
> > unique numbers.
> > 
> > In the rare cases of collision, we will detect and find another number
> > that is not in use.
> > Thanks to Michael Kelley [ref] for proposing this idea.

> > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> 
> Acked-by: Sasha Levin <sashal@kernel.org>
> 
> Bjorn, will you take it through the PCI tree or do you want me to take
> it through hyper-v?

Lorenzo usually applies patches to drivers/pci/controller/*, so that
would be my preference.

Bjorn
```