Re: [PATCH V4 mlx5-next 11/13] vfio/mlx5: Implement vfio_pci driver for mlx5 devices

Alex Williamson
2021-10-26T22:42:37Z

On Tue, 26 Oct 2021 12:06:03 +0300
Yishai Hadas <yishaih@nvidia.com> wrote:
> +static int mlx5vf_pci_set_device_state(struct mlx5vf_pci_core_device *mvdev,
> + u32 state)
> +{
> + struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
> + u32 old_state = vmig->vfio_dev_state;
> + u32 flipped_bits = old_state ^ state;
> + int ret = 0;
> +
> + if (old_state == VFIO_DEVICE_STATE_ERROR ||
> + !VFIO_DEVICE_STATE_VALID(state) ||
> + (state & ~MLX5VF_SUPPORTED_DEVICE_STATES))
> + return -EINVAL;
> +
> + /* Running switches off */
> + if ((flipped_bits & VFIO_DEVICE_STATE_RUNNING) &&
> + !(state & VFIO_DEVICE_STATE_RUNNING)) {
> + ret = mlx5vf_pci_quiesce_device(mvdev);
> + if (ret)
> + return ret;
> + ret = mlx5vf_pci_freeze_device(mvdev);
> + if (ret) {
> + vmig->vfio_dev_state = VFIO_DEVICE_STATE_ERROR;
> + return ret;

Is it not possible for this to unwind, only entering the error state if
unquiesce also fails?

> + }
> + }
> +
> + /* Saving switches on and not running */
> + if ((flipped_bits &
> + (VFIO_DEVICE_STATE_RUNNING | VFIO_DEVICE_STATE_SAVING)) &&
> + ((state & (VFIO_DEVICE_STATE_RUNNING |
> + VFIO_DEVICE_STATE_SAVING)) == VFIO_DEVICE_STATE_SAVING)) {

Can't this be reduced to:

if ((flipped_bits & ~VFIO_DEVICE_STATE_RESUMING) &&
(state == VFIO_DEVICE_STATE_SAVING)) {

Maybe there's an argument for the original to be more invariant of TBD
device_state bits? Thanks,

Alex

> + ret = mlx5vf_pci_save_device_data(mvdev);
> + if (ret)
> + return ret;
> + }
> +
> + /* Resuming switches on */
> + if ((flipped_bits & VFIO_DEVICE_STATE_RESUMING) &&
> + (state & VFIO_DEVICE_STATE_RESUMING)) {
> + mlx5vf_reset_mig_state(mvdev);
> + ret = mlx5vf_pci_new_write_window(mvdev);
> + if (ret)
> + return ret;
> + }
> +
> + /* Resuming switches off */
> + if ((flipped_bits & VFIO_DEVICE_STATE_RESUMING) &&
> + !(state & VFIO_DEVICE_STATE_RESUMING)) {
> + /* deserialize state into the device */
> + ret = mlx5vf_load_state(mvdev);
> + if (ret) {
> + vmig->vfio_dev_state = VFIO_DEVICE_STATE_ERROR;
> + return ret;
> + }
> + }
> +
> + /* Running switches on */
> + if ((flipped_bits & VFIO_DEVICE_STATE_RUNNING) &&
> + (state & VFIO_DEVICE_STATE_RUNNING)) {
> + ret = mlx5vf_pci_unfreeze_device(mvdev);
> + if (ret)
> + return ret;
> + ret = mlx5vf_pci_unquiesce_device(mvdev);
> + if (ret) {
> + vmig->vfio_dev_state = VFIO_DEVICE_STATE_ERROR;
> + return ret;
> + }
> + }
> +
> + vmig->vfio_dev_state = state;
> + return 0;
> +}