Virtio-GPU S4 support

From: Dongwon Kim <dongwon.kim@intel.com>

This patch series implements functions for .freeze and .restore hooks for
virtio-gpu driver as well as pm-notifier to handle object restoration in
S4(hiberation) case.

First patch adds `virtgpu_freeze` and `virtgpu_restore` functions.
These functions handle the deletion of virtio queues before suspension and
their recreation during the restoration process.

Second patch implements a mechanism for restoring `virtio_gpu_object` instances.
This is necessary because the host (QEMU) deletes all associated resources during
the virtio-gpu reset, which occurs as part of hiberation/resume process.

Third patch adds pm-notifier to the driver that handles resubmission of virtio-gpu
objects to the QEMU once the guest resumes from hibenation.

These changes ensure that the virtio-gpu driver can properly handle hibernation
scenarios without resource loss.

v2: 10ms sleep is added in virtgpu_freeze to avoid the situation
    the driver is locked up during resumption.

v3: Plain 10ms delay (v2) is replaced with wait calls which wait until
    the virtio queue is empty.
    (Dmitry Osipenko)

v4: New version of patchset only covers S4 case because loss of resources in S3
    case can be avoided by skipping virtio-gpu-reset in QEMU (hw/display/virtio-gpu.c).
    To skip virtio-gpu-reset (soft-reset), virtio-gpu-pci device should be attached to
    PCIE bus AND a PCIE option, 'x-pcie-pm-no-soft-reset' should added and set to 'true'.
    (e.g. -device virtio-gpu-pci,bus=port,x-pcie-pm-no-soft-reset=true)

v5: Remove virtio_gpu_object from the restore list before freeing the object
    to prevent an use-after-free situation.
    (Nirmoy Das)

    Protect restore list operations with a spinlock
    (Nirmoy Das)

    Move restore list node into virtio_gpu_bo struct to reduce memory usage
    (Dmitry Osipenko)

    Remove unused header - drm_atomic_helper.h
    (Dmitry Osipenko)

v6: Include object backed by imported dmabuf
    (Dmitry Osipenko)

    Not storing virgl objects in the restore_list as virgl 3D objects are not
    recoverable.
    (Dmitry Osipenko)

    Change the name 'list',a node in restore_list to 'restore_node'
    (Nirmoy Das)

    Use mutex instead of spinlock when updating restore_list
    (Nirmoy Das)

    Initialize restore_node when virtio_gpu_object is created - this is to
    check if the node is in the list with 'list_empty' before removing it.

    Restoring objects in the PM notifier is too late, as virtio-gpu
    message communication begins in virtgpu_restore once virtqueues
    are re-established. To address this, a 'hibernation' flag is set
    during the PM_HIBERNATION_PREPARE phase in the notifier. This flag
    is then used in virtgpu_restore to detect if the system is resuming
    from S4, allowing objects to be recovered immediately after virtqueues
    are reconfigured.

Dongwon Kim (3):
  drm/virtio: Freeze and restore hooks to support suspend and resume
  drm/virtio: Add support for saving and restoring virtio_gpu_objects
  drm/virtio: Add PM notifier to restore objects after hibernation

 drivers/gpu/drm/virtio/virtgpu_drv.c    | 69 ++++++++++++++++++++++++-
 drivers/gpu/drm/virtio/virtgpu_drv.h    | 15 ++++++
 drivers/gpu/drm/virtio/virtgpu_kms.c    | 53 ++++++++++++++++---
 drivers/gpu/drm/virtio/virtgpu_object.c | 59 +++++++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_prime.c  | 44 ++++++++++++++++
 drivers/gpu/drm/virtio/virtgpu_vram.c   |  2 +
 6 files changed, 235 insertions(+), 7 deletions(-)

-- 
2.34.1