[PATCH v3 0/1] Define low power mode for devices

[David Stevens <stevensd@chromium.org>]

The virtio spec currently does not include the concept of device power
management. The lack means that there is no good action drivers can take
when they are requested to put the device into a low power state (e.g.
when a guest is entering a system-wide low power state like S0ix/S3).
Stateless devices can be handled - albeit inefficiently - by resetting
and reinitialzing the device. However, stateful devices cannot support
this situation. This patch defines a low power mode for devices that can
be used in this situation.

Low power mode is mostly defined at the transport layer, and all
device-side power optimizations are optional. This avoids the need for
invasive device-by-device definitions. It also pushes the requirement
onto the device side, to simplify what driver side changes are
necessary to just [1].

I believe this patch may address the virtio-gpu issue which [2] is
trying to address by avoiding the reset altogether when the guest enters
S3.

[1] https://lore.kernel.org/lkml/20231113055138.117392-1-stevensd@chromium.org/
[2] https://lore.kernel.org/lkml/20230919114242.2283646-1-Jiqian.Chen@amd.com/

v2 -> v3:
 - Use different words for some concepts to avoid conflicts with other
   parts of the spec.
 - Rewrite various sentences to improve clarity.
v1 -> v2:
 - Define virtio-pci support on top of PCI power management.
 - Add more conformance requirements.

David Stevens (1):
  Define a low power mode for devices

 content.tex       | 61 +++++++++++++++++++++++++++++++++++++++++++++++
 transport-pci.tex |  9 +++++++
 2 files changed, 70 insertions(+)

-- 
2.43.0.rc2.451.g8631bc7472-goog