linux-kernel - Re: [PATCH vhost v4 14/15] vdpa/mlx5: Introduce reference counting to mrs

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Date: Wed, 20 Dec 2023 11:47:08 +0800
From: Jason Wang <jasowang@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Eugenio Perez Martin <eperezma@...hat.com>, 
	Si-Wei Liu <si-wei.liu@...cle.com>, Saeed Mahameed <saeedm@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, virtualization@...ts.linux-foundation.org, 
	Gal Pressman <gal@...dia.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Parav Pandit <parav@...dia.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH vhost v4 14/15] vdpa/mlx5: Introduce reference counting to mrs

On Wed, Dec 20, 2023 at 2:10 AM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> Deleting the old mr during mr update (.set_map) and then modifying the
> vqs with the new mr is not a good flow for firmware. The firmware
> expects that mkeys are deleted after there are no more vqs referencing
> them.
>
> Introduce reference counting for mrs to fix this. It is the only way to
> make sure that mkeys are not in use by vqs.
>
> An mr reference is taken when the mr is associated to the mr asid table
> and when the mr is linked to the vq on create/modify. The reference is
> released when the mkey is unlinked from the vq (trough modify/destroy)
> and from the mr asid table.
>
> To make things consistent, get rid of mlx5_vdpa_destroy_mr and use
> get/put semantics everywhere.
>
> Reviewed-by: Gal Pressman <gal@...dia.com>
> Acked-by: Eugenio Pérez <eperezma@...hat.com>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> ---

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks