[PATCH v6 00/11] Implement forced unplug and forced activation

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

The goal of these two features is to simplify driver servicing and avoid
requiring storing driver state in Registry.

Forced unplug, as name implies, forcefully unplugs emulated devices when
a driver is present, rather than when it's active. It defines a Registry
key at CurrentControlSet\XEN\ForceUnplug. Drivers can opt into forced
unplug by creating an appropriate value (DISKS/NICS) in this key.

Note that since it's no longer possible to guarantee removal of Registry
values during driver uninstallation by Windows, driver uninstallers are
expected to remove these values themselves.

Forced activation is the companion to forced unplug. It aims to make
activation of Xenbus FDOs deterministic and stateless, using a
precedence mapping based on device IDs, prioritizing the vendor device
over the generic ones. This avoids situations where the wrong FDO is
activated, which will prevent Windows Update from working.

Like forced unplug, the precedence mapping of forced activation is also
expected to be removed by driver uninstallers.

With forced activation, Xenfilt is now installed via INF on top of the
current installation routines. This means PV drivers can be injected
offline without needing another reboot to be reconfigured.

Care is taken to keep compatibility with older drivers. The two features
are also conditioned behind new build environment variables FORCE_UNPLUG
and FORCE_ACTIVATE.

Forced activation introduces EMULATED v3 and PDO revision 0x0900000C.
Deprecate PDO revisions 0x09000007 and earlier to make room for the new
revision.
Xenvif 0x09000000 is also removed due to the deprecation of CACHE v1.

With forced unplug/activation, the whole boot chain of boot-critical
drivers must be available in the driver store to avoid
INACCESSIBLE_BOOT_DEVICE BSOD. Fix this issue by merging all hardware
IDs into one INF Models entry.

Finally, since forced activation can cause the active device to change
without prior notice, such a change will cause old drivers to lose their
bindings due to a change in the device instance path. Drop the vendor
device ID from DeviceID to make sure that device instance paths remain
stable across vendor device changes.

The following scenarios have been successfully tested, requiring only
one reboot each:
* Offline driver installation via DISM
* Fresh install, followed by switching from device 0001 to 0002
* Fresh install, followed by toggling vendor device
* Xenbus/Xenvbd update

Other tested scenarios:
* Mixing of old Xenbus and new Xenvbd (and vice versa) while toggling
  device ID (v4)
* Major OS upgrade (Windows 10 22H2 -> Windows 11 24H2)

Commit notes:
* Patch 1 "Collapse skipped template lines" is for all repos.
* These forced-activation commits are linked and cannot be separated:
  * xenfilt: Add Xenbus device precedence mechanism
  * Add EMULATED v3
  * Use EMULATED v3 to force activate Xenbus FDOs

Changes in v6:
* Fixed logic in "Collapse skipped template lines"
* Moved precedence values to their own key xenfilt\Parameters\Precedence
* Changed INFs to promote 0002 device to hardware ID in Models entry if
  vendor device support is not present to avoid Inf2Cat 22.9.3 warning
* Fixed emulated.h still using LONG ForceActivate

v5: Ad-hoc patches to v4, see v6

Changes in v4:
* Restored interfaces deprecated in v3 to allow old drivers to work with
  existing binding, while still removing old PDO revisions
* Converted IsForceActivated LONG value to a proper enum
* Stripped vendor device ID from device ID strings
  * The same was done for Xencons, Xenvif and Xenvkbd
* Fixed mistakenly-left-in DEV_C000 in forced-activation Xenbus.inf
* Moved PdoGetPrecedence to driver.c and merged into DriverGetPrecedence
* Refactored EmulatedIsDevicePresent condition checking
* Removed Xenvif revision 0x09000000 due to the deprecation of CACHE v1

v3: 
https://lists.xenproject.org/archives/html/win-pv-devel/2025-08/msg00002.html
* Deprecated PDO revisions 0x09000007 and earlier to make room for
  0x0900000C
* Merged all hardware IDs into one INF Models entry to avoid BSODs when
  changing platform device IDs and toggling vendor device
* Added a note mentioning the role of driver uninstallers in cleanup of
  forced unplug/activation drivers.

v2: 
https://lists.xenproject.org/archives/html/win-pv-devel/2025-07/msg00053.html
* Added forced activation

v1: 
https://lists.xenproject.org/archives/html/win-pv-devel/2025-07/msg00012.html

Tu Dinh (11):
  Collapse skipped template lines
  Merge all hardware IDs into one Models entry
  Remove vendor device ID from DeviceID
  Deprecate PDO revisions 0x09000007 and earlier
  xenbus: Use nonpaged pool in FdoQueryId
  Add forced unplug support
  xenfilt: Add Xenbus device precedence mechanism
  Add EMULATED v3
  Use EMULATED v3 to force activate Xenbus FDOs
  Enable Xenbus precedence
  Install Xenfilt with INF AddReg

 include/emulated_interface.h |  61 +++++++++++++---
 include/revision.h           |  11 +--
 scripts/genfiles.ps1         |  15 ++--
 src/xen/driver.c             |  79 ++++++++++++++++-----
 src/xen/driver.h             |   5 ++
 src/xen/unplug.c             |  13 +++-
 src/xenbus.inf               |  25 ++++---
 src/xenbus/fdo.c             | 134 ++++++++++++++++++++++++-----------
 src/xenbus/pdo.c             |   3 +-
 src/xenfilt/driver.c         |  93 ++++++++++++++++++++++--
 src/xenfilt/driver.h         |   7 ++
 src/xenfilt/emulated.c       | 115 ++++++++++++++++++++++++------
 src/xenfilt/emulated.h       |  13 ++--
 src/xenfilt/fdo.c            |  30 +++++++-
 src/xenfilt/pdo.c            |  63 ++++++++--------
 src/xenfilt/pdo.h            |   7 +-
 16 files changed, 514 insertions(+), 160 deletions(-)

--
2.50.1.windows.1


Ngoc Tu Dinh | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech