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

[Xueming Li]

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.

Signed-off-by: Xueming Li <xuemingl at nvidia.com>
Reviewed-by: Matan Azrad <matan at 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 6d17d7a6f3..991739e984 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;
-- 
2.33.0