On Wed, 2021-10-13 at 12:06 +0200, Maxime Coquelin wrote:
>
> On 9/23/21 10:17, 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.
> >
> > Signed-off-by: Xueming Li <xuemi...@nvidia.com>
> > Reviewed-by: Matan Azrad <ma...@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;
> >
>
> That looks fragile, but at least we have a warning we can rely on.
> Shouldn't we have a way to wait for Qemu to release the resources at
> vdpa driver shutdown time?
If dpdk-vdpa get killed and restart, qemu will shutdown device and
unmap the resources independently.
>
> Also as on patch 1, please add a Fixes tag it you want it to be
> backported.
Agree to backport, but not a fix, I'll add cc:sta...@dpdk.org, the
patch will be noticed by maintainer, thanks for the suggestion!
>
> Regards,
> Maxime
>
