Re: [PATCH vhost v2 03/10] vdpa/mlx5: Introduce async fw command wrapper

[Eugenio Perez Martin]

On Fri, Aug 16, 2024 at 11:02 AM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
>
> Introduce a new function mlx5_vdpa_exec_async_cmds() which
> wraps the mlx5_core async firmware command API in a way
> that will be used to parallelize certain operation in this
> driver.
>
> The wrapper deals with the case when mlx5_cmd_exec_cb() returns
> EBUSY due to the command being throttled.
>
> Signed-off-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>

Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>

> ---
>  drivers/vdpa/mlx5/core/mlx5_vdpa.h | 15 ++++++
>  drivers/vdpa/mlx5/core/resources.c | 73 ++++++++++++++++++++++++++++++
>  2 files changed, 88 insertions(+)
>
> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> index 424d445ebee4..b34e9b93d56e 100644
> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
> @@ -105,6 +105,18 @@ struct mlx5_vdpa_dev {
>         bool suspended;
>  };
>
> +struct mlx5_vdpa_async_cmd {
> +       int err;
> +       struct mlx5_async_work cb_work;
> +       struct completion cmd_done;
> +
> +       void *in;
> +       size_t inlen;
> +
> +       void *out;
> +       size_t outlen;
> +};
> +
>  int mlx5_vdpa_create_tis(struct mlx5_vdpa_dev *mvdev, void *in, u32 *tisn);
>  void mlx5_vdpa_destroy_tis(struct mlx5_vdpa_dev *mvdev, u32 tisn);
>  int mlx5_vdpa_create_rqt(struct mlx5_vdpa_dev *mvdev, void *in, int inlen, u32 *rqtn);
> @@ -134,6 +146,9 @@ int mlx5_vdpa_update_cvq_iotlb(struct mlx5_vdpa_dev *mvdev,
>                                 unsigned int asid);
>  int mlx5_vdpa_create_dma_mr(struct mlx5_vdpa_dev *mvdev);
>  int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
> +int mlx5_vdpa_exec_async_cmds(struct mlx5_vdpa_dev *mvdev,
> +                             struct mlx5_vdpa_async_cmd *cmds,
> +                             int num_cmds);
>
>  #define mlx5_vdpa_err(__dev, format, ...)                                                          \
>         dev_err((__dev)->mdev->device, "%s:%d:(pid %d) error: " format, __func__, __LINE__,        \
> diff --git a/drivers/vdpa/mlx5/core/resources.c b/drivers/vdpa/mlx5/core/resources.c
> index 5c5a41b64bfc..22ea32fe007b 100644
> --- a/drivers/vdpa/mlx5/core/resources.c
> +++ b/drivers/vdpa/mlx5/core/resources.c
> @@ -321,3 +321,76 @@ void mlx5_vdpa_free_resources(struct mlx5_vdpa_dev *mvdev)
>         mutex_destroy(&mvdev->mr_mtx);
>         res->valid = false;
>  }
> +
> +static void virtqueue_cmd_callback(int status, struct mlx5_async_work *context)
> +{
> +       struct mlx5_vdpa_async_cmd *cmd =
> +               container_of(context, struct mlx5_vdpa_async_cmd, cb_work);
> +
> +       cmd->err = mlx5_cmd_check(context->ctx->dev, status, cmd->in, cmd->out);
> +       complete(&cmd->cmd_done);
> +}
> +
> +static int issue_async_cmd(struct mlx5_vdpa_dev *mvdev,
> +                          struct mlx5_vdpa_async_cmd *cmds,
> +                          int issued,
> +                          int *completed)
> +
> +{
> +       struct mlx5_vdpa_async_cmd *cmd = &cmds[issued];
> +       int err;
> +
> +retry:
> +       err = mlx5_cmd_exec_cb(&mvdev->async_ctx,
> +                              cmd->in, cmd->inlen,
> +                              cmd->out, cmd->outlen,
> +                              virtqueue_cmd_callback,
> +                              &cmd->cb_work);
> +       if (err == -EBUSY) {
> +               if (*completed < issued) {
> +                       /* Throttled by own commands: wait for oldest completion. */
> +                       wait_for_completion(&cmds[*completed].cmd_done);
> +                       (*completed)++;
> +
> +                       goto retry;
> +               } else {
> +                       /* Throttled by external commands: switch to sync api. */
> +                       err = mlx5_cmd_exec(mvdev->mdev,
> +                                           cmd->in, cmd->inlen,
> +                                           cmd->out, cmd->outlen);
> +                       if (!err)
> +                               (*completed)++;
> +               }
> +       }
> +
> +       return err;
> +}
> +
> +int mlx5_vdpa_exec_async_cmds(struct mlx5_vdpa_dev *mvdev,
> +                             struct mlx5_vdpa_async_cmd *cmds,
> +                             int num_cmds)
> +{
> +       int completed = 0;
> +       int issued = 0;
> +       int err = 0;
> +
> +       for (int i = 0; i < num_cmds; i++)
> +               init_completion(&cmds[i].cmd_done);
> +
> +       while (issued < num_cmds) {
> +
> +               err = issue_async_cmd(mvdev, cmds, issued, &completed);
> +               if (err) {
> +                       mlx5_vdpa_err(mvdev, "error issuing command %d of %d: %d\n",
> +                                     issued, num_cmds, err);
> +                       break;
> +               }
> +
> +               issued++;
> +       }
> +
> +       while (completed < issued)
> +               wait_for_completion(&cmds[completed++].cmd_done);
> +
> +       return err;
> +}
> --
> 2.45.1
>