Re: [PATCH v2 0/7] Implement forced unplug and forced activation

["Tu Dinh" <ngoc-tu.dinh@xxxxxxxxxx>]

On 31/07/2025 16:26, Owen Smith wrote:
> Having played with this a bit, there seems to be several edge cases that 
> are fatal.
> 1) installing on 1 device (e.g. 0002) without any others seems to work. 
> Shutting down, and changing the device (e.g. to 0001) and booting, will 
> trigger an 0x7B bugcheck (emulated disk is unplugged, but the PV disk 
> has not bound to the 0001 device nodes)
> 2) installing on 1 device (e.g. 0002), shutting down and adding the 
> vendor device will trigger a 0x7B bugcheck on boot (as the emulated disk 
> is unplugged, but the driver stack has not reinstalled on the vendor device)
> There may well be more problem cases, but I've not investigated further.
> 
> Owen
> 

It's something I've been looking at as well.

Basically, when the driver is installed online, it will only populate 
the registry keys 
HKLM\SYSTEM\DriverDatabase\DriverPackages\xenbus.inf_*\Descriptors\PCI\*
corresponding to the active device.
Once another device is installed, Windows is unable to pick up and 
install the driver. So forced unplug/activation and vendor device 
binding are incompatible at the moment.

Interestingly, the problem will not exist when the driver is installed 
offline via Dism, as it will populate the registry with all the 
supported device IDs.

One way to fix this is to (only when forced unplug/activation is set):
- make xenbus.inf bind to PCI\VEN_5853 or something equivalent instead 
of a list of branded device IDs;
- for each child PDO, add a compatible ID without the vendor device ID 
(e.g. XENBUS\VEN_@VENDOR_PREFIX@&DEV_VBD&REV_0900000B);
- make xenvbd.inf bind to that compatible ID

This should make sure that the full driver chain is available during 
boot time, at the cost of potentially breaking Windows Update delivery.

I've tested this on Server 2022 and it seems to work.

Related: 
https://community.osr.com/t/hklm-system-driverdatabase-driverpackages-bus-driver-inf-not-properly-configured/52214


Ngoc Tu Dinh | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech