Re: [dpdk-stable] [PATCH v2 2/2] vdpa/mlx5: retry VAR allocation during vDPA restart

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 10/15/21 17:05, Xueming Li wrote:
> VAR is the device memory space for the virtio queues doorbells, qemu
> could mmap it to directly to speed up doorbell push.
> 
> On a busy system, Qemu takes time to release VAR resources during driver
> shutdown. If vdpa restarted quickly, the VAR allocation failed with
> error 28 since the VAR is singleton resource per device.
> 
> This patch adds retry mechanism for VAR allocation.
> 
> Fixes: 4cae722c1b06 ("vdpa/mlx5: move virtual doorbell alloc to probe")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Xueming Li <xuemingl@nvidia.com>
> Reviewed-by: Matan Azrad <matan@nvidia.com>
> ---
>   drivers/vdpa/mlx5/mlx5_vdpa.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/mlx5/mlx5_vdpa.c b/drivers/vdpa/mlx5/mlx5_vdpa.c
> index 6d17d7a6f3e..991739e9840 100644
> --- a/drivers/vdpa/mlx5/mlx5_vdpa.c
> +++ b/drivers/vdpa/mlx5/mlx5_vdpa.c
> @@ -693,7 +693,14 @@ mlx5_vdpa_dev_probe(struct rte_device *dev)
>   	if (attr.num_lag_ports == 0)
>   		priv->num_lag_ports = 1;
>   	priv->ctx = ctx;
> -	priv->var = mlx5_glue->dv_alloc_var(ctx, 0);
> +	for (retry = 0; retry < 7; retry++) {
> +		priv->var = mlx5_glue->dv_alloc_var(ctx, 0);
> +		if (priv->var != NULL)
> +			break;
> +		DRV_LOG(WARNING, "Failed to allocate VAR, retry %d.\n", retry);
> +		/* Wait Qemu release VAR during vdpa restart, 0.1 sec based. */
> +		usleep(100000U << retry);
> +	}
>   	if (!priv->var) {
>   		DRV_LOG(ERR, "Failed to allocate VAR %u.", errno);
>   		goto error;
> 

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime