linux-kernel - Re: [PATCH v1] dmaengine: idxd: drain ATS translations when disabling WQ

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Message-ID: <e89ea10b-edb5-4e37-8eef-0fb99fc5b19f@intel.com>
Date: Wed, 1 Oct 2025 08:42:04 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>, dmaengine@...r.kernel.org
Cc: vkoul@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: idxd: drain ATS translations when disabling
 WQ



On 9/30/25 6:22 PM, Vinicius Costa Gomes wrote:
> From: Nikhil Rao <nikhil.rao@...el.com>
> 
> There's an errata[1], for the Disable WQ command that it
> does not guaranteee that address translations are drained. If WQ
> configuration is updated, pending address translations can use an
> updated WQ configuration, resulting an invalid translation response
> that is cached in the device translation cache.
> 
> Replace the Disable WQ command with a Drain WQ command followed by a
> Reset WQ command, this guarantees that all ATS translations are
> drained from the device before changing WQ configuration.
> 
> [1] https://cdrdv2.intel.com/v1/dl/getcontent/843306 ("Intel DSA May
> Cause Invalid Translation Caching")
> 
> Signed-off-by: Nikhil Rao <nikhil.rao@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
>  drivers/dma/idxd/device.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
> index 5cf419fe6b46..c2cdf41b6e57 100644
> --- a/drivers/dma/idxd/device.c
> +++ b/drivers/dma/idxd/device.c
> @@ -16,6 +16,7 @@ static void idxd_cmd_exec(struct idxd_device *idxd, int cmd_code, u32 operand,
>  			  u32 *status);
>  static void idxd_device_wqs_clear_state(struct idxd_device *idxd);
>  static void idxd_wq_disable_cleanup(struct idxd_wq *wq);
> +static int idxd_wq_config_write(struct idxd_wq *wq);
>  
>  /* Interrupt control bits */
>  void idxd_unmask_error_interrupts(struct idxd_device *idxd)
> @@ -215,14 +216,28 @@ int idxd_wq_disable(struct idxd_wq *wq, bool reset_config)
>  		return 0;
>  	}
>  
> +	/*
> +	 * Disable WQ does not drain address translations, if WQ attributes are
> +	 * changed before translations are drained, pending translations can
> +	 * be issued using updated WQ attibutes, resulting in invalid
> +	 * translations being cached in the device translation cache.
> +	 *
> +	 * To make sure pending translations are drained before WQ
> +	 * attributes are changed, we use a WQ Drain followed by WQ Reset and
> +	 * then restore the WQ configuration.
> +	 */
> +	idxd_wq_drain(wq);
> +
>  	operand = BIT(wq->id % 16) | ((wq->id / 16) << 16);
> -	idxd_cmd_exec(idxd, IDXD_CMD_DISABLE_WQ, operand, &status);
> +	idxd_cmd_exec(idxd, IDXD_CMD_RESET_WQ, operand, &status);
>  
>  	if (status != IDXD_CMDSTS_SUCCESS) {
> -		dev_dbg(dev, "WQ disable failed: %#x\n", status);
> +		dev_dbg(dev, "WQ reset failed: %#x\n", status);
>  		return -ENXIO;
>  	}
>  
> +	idxd_wq_config_write(wq);
> +
>  	if (reset_config)
>  		idxd_wq_disable_cleanup(wq);
>  	clear_bit(wq->id, idxd->wq_enable_map);