linux-kernel - Re: [PATCH v4 1/2] dmaengine: idxd: Protect int

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Message-ID: <5dca6853-cd14-a8fc-ce1b-b64b1b8b3412@intel.com>
Date:   Tue, 31 Oct 2023 10:57:46 -0500
From:   Lijun Pan <lijun.pan@...el.com>
To:     'Guanjun' <guanjun@...ux.alibaba.com>, <dave.jiang@...el.com>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <vkoul@...nel.org>, <tony.luck@...el.com>, <fenghua.yu@...el.com>
CC:     <jing.lin@...el.com>, <ashok.raj@...el.com>,
        <sanjay.k.kumar@...el.com>, <megha.dey@...el.com>,
        <jacob.jun.pan@...el.com>, <yi.l.liu@...el.com>,
        <tglx@...utronix.de>
Subject: Re: [PATCH v4 1/2] dmaengine: idxd: Protect int_handle field in hw
 descriptor



On 10/30/2023 9:55 PM, 'Guanjun' wrote:
> From: Guanjun <guanjun@...ux.alibaba.com>
> 
> The int_handle field in hw descriptor should also be protected
> by wmb() before possibly triggering a DMA read.
> 
> Fixes: ec0d64231615 (dmaengine: idxd: embed irq_entry in idxd_wq struct)

I think the direct fix is to eb0cf33a91b4 which moves the interrupt 
handle assignment to idxd_submit_desc() and has a write to 
desc->hw->int_handle before submission of desc->hw.

Fixes: eb0cf33a91b4 ("dmaengine: idxd: move interrupt handle assignment")

Other than that,
Reviewed-by: Lijun Pan <lijun.pan@...el.com>


> Signed-off-by: Guanjun <guanjun@...ux.alibaba.com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>   drivers/dma/idxd/submit.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dma/idxd/submit.c b/drivers/dma/idxd/submit.c
> index c01db23e3333..3f922518e3a5 100644
> --- a/drivers/dma/idxd/submit.c
> +++ b/drivers/dma/idxd/submit.c
> @@ -182,13 +182,6 @@ int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
>   
>   	portal = idxd_wq_portal_addr(wq);
>   
> -	/*
> -	 * The wmb() flushes writes to coherent DMA data before
> -	 * possibly triggering a DMA read. The wmb() is necessary
> -	 * even on UP because the recipient is a device.
> -	 */
> -	wmb();
> -
>   	/*
>   	 * Pending the descriptor to the lockless list for the irq_entry
>   	 * that we designated the descriptor to.
> @@ -199,6 +192,13 @@ int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
>   		llist_add(&desc->llnode, &ie->pending_llist);
>   	}
>   
> +	/*
> +	 * The wmb() flushes writes to coherent DMA data before
> +	 * possibly triggering a DMA read. The wmb() is necessary
> +	 * even on UP because the recipient is a device.
> +	 */
> +	wmb();
> +
>   	if (wq_dedicated(wq)) {
>   		iosubmit_cmds512(portal, desc->hw, 1);
>   	} else {