RE: [PATCH v2] PCI: hv: Detect and fix Hyper-V PCI domain number collision

[Haiyang Zhang <haiyangz@microsoft.com>]

> -----Original Message-----
> From: LKML haiyangz <lkmlhyz@microsoft.com> On Behalf Of Haiyang
> Zhang
> Sent: Tuesday, August 6, 2019 7:52 PM
> To: sashal@kernel.org; bhelgaas@google.com; lorenzo.pieralisi@arm.com;
> linux-hyperv@vger.kernel.org; linux-pci@vger.kernel.org
> Cc: Haiyang Zhang <haiyangz@microsoft.com>; KY Srinivasan
> <kys@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com>;
> olaf@aepfle.de; vkuznets <vkuznets@redhat.com>; linux-
> kernel@vger.kernel.org
> Subject: [PATCH v2] PCI: hv: Detect and fix Hyper-V PCI domain number
> collision
> 
> Currently in Azure cloud, for passthrough devices including GPU, the
> host sets the device instance ID's bytes 8 - 15 to a value derived from
> the host HWID, which is the same on all devices in a VM. So, the device
> instance ID's bytes 8 and 9 provided by the host are no longer unique.
> 
> This can cause device passthrough to VMs to fail because the bytes 8 and
> 9 is used as PCI domain number. So, as recommended by Azure host team,
> we now use the bytes 4 and 5 which usually contain unique numbers as PCI
> domain. The chance of collision is greatly reduced. In the rare cases of
> collision, we will detect and find another number that is not in use.
> 
> Thanks to Michael Kelley <mikelley@microsoft.com> for proposing this idea.
> 
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> Acked-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/pci/controller/pci-hyperv.c | 92

Hi Lorenzo,

This patch has been updated based on Bjorn's comments. Do you have any further
comments? Could you take it from your tree?

Thanks,
- Haiyang