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Message-ID: <2d6a1063-34ad-70ca-3d1c-0be2143ff3f4@redhat.com>
Date:   Tue, 9 May 2023 10:38:51 +0200
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Subject: Re: [PATCH v1 1/1] platform/mellanox: fix potential race in
 mlxbf-tmfifo driver
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To:     Liming Sun <limings@nvidia.com>,
        Vadim Pasternak <vadimp@nvidia.com>,
        David Thompson <davthompson@nvidia.com>,
        Mark Gross <markgross@kernel.org>
Cc:     platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
References: <b98c0ab61d644ba38fa9b3fd1607b138b0dd820b.1682518748.git.limings@nvidia.com>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <b98c0ab61d644ba38fa9b3fd1607b138b0dd820b.1682518748.git.limings@nvidia.com>
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Vadim,

On 4/26/23 16:23, Liming Sun wrote:
> This commit adds memory barrier for the 'vq' update in function
> mlxbf_tmfifo_virtio_find_vqs() to avoid potential race due to
> out-of-order memory write. It also adds barrier for the 'is_ready'
> flag to make sure the initializations are visible before this flag
> is checked.
> 
> Signed-off-by: Liming Sun <limings@nvidia.com>

Can you review this patch please ?

Regards,

Hans


> ---
>  drivers/platform/mellanox/mlxbf-tmfifo.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
> index 91a077c35b8b..a79318e90a13 100644
> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> @@ -784,7 +784,7 @@ static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
>  	fifo = vring->fifo;
>  
>  	/* Return if vdev is not ready. */
> -	if (!fifo->vdev[devid])
> +	if (!fifo || !fifo->vdev[devid])
>  		return;
>  
>  	/* Return if another vring is running. */
> @@ -980,9 +980,13 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
>  
>  		vq->num_max = vring->num;
>  
> +		vq->priv = vring;
> +
> +		/* Make vq update visible before using it. */
> +		virtio_mb(false);
> +
>  		vqs[i] = vq;
>  		vring->vq = vq;
> -		vq->priv = vring;
>  	}
>  
>  	return 0;
> @@ -1302,6 +1306,9 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev)
>  
>  	mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
>  
> +	/* Make all updates visible before setting the 'is_ready' flag. */
> +	virtio_mb(false);
> +
>  	fifo->is_ready = true;
>  	return 0;
>