Re: [PATCH v2 0/1] Define low power mode for devices

[David Stevens <stevensd@chromium.org>]

On Mon, Nov 13, 2023 at 3:20âPM David Stevens <stevensd@chromium.org> wrote:
>
> 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/
>
> v1 -> v2:
>  - Define virtio-pci support on top of PCI power management.
>  - Add more conformance requirements.

Friendly ping, and directly CC'ing reviewers.

-David