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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Nov 13, 2023 at 03:19:49PM +0900, David Stevens 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].

Great idea.
This couldn't have come at a better time, too.
Please do remember to CC reviewers directly in the future, though.


> 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.
> 
> David Stevens (1):
>   Define a low power mode for devices
> 
>  content.tex       | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  transport-pci.tex |  7 +++++++
>  2 files changed, 52 insertions(+)
> 
> -- 
> 2.42.0.869.gea05f2083d-goog
> 
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