linux-kernel - Re: [PATCH v1] dmaengine: idxd: Narrow the restriction on BATCH to ver. 1 only

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Message-ID: <a1b7d7d8-4fc0-4faf-9938-57ccd1b861ab@nvidia.com>
Date: Wed, 2 Apr 2025 17:57:44 -0700
From: Fenghua Yu <fenghuay@...dia.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 Dave Jiang <dave.jiang@...el.com>, Vinod Koul <vkoul@...nel.org>,
 dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>
Subject: Re: [PATCH v1] dmaengine: idxd: Narrow the restriction on BATCH to
 ver. 1 only

Hi, Vinicius,

On 3/12/25 15:15, Vinicius Costa Gomes wrote:
> Allow BATCH operations to be submitted and the capability to be
> exposed for DSA version 2 (or later) devices.
>
> DSA version 2 devices allow safe submission of BATCH operations.
>
> Signed-off-by: Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---
>   drivers/dma/idxd/cdev.c  | 6 ++++--
>   drivers/dma/idxd/sysfs.c | 6 ++++--
>   2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
> index ff94ee892339..6a1dc15ee485 100644
> --- a/drivers/dma/idxd/cdev.c
> +++ b/drivers/dma/idxd/cdev.c
> @@ -439,10 +439,12 @@ static int idxd_submit_user_descriptor(struct idxd_user_context *ctx,
>   	 * DSA devices are capable of indirect ("batch") command submission.
>   	 * On devices where direct user submissions are not safe, we cannot
>   	 * allow this since there is no good way for us to verify these
> -	 * indirect commands.
> +	 * indirect commands. Narrow the restriction of operations with the
> +	 * BATCH opcode to only DSA version 1 devices.
>   	 */
>   	if (is_dsa_dev(idxd_dev) && descriptor.opcode == DSA_OPCODE_BATCH &&
> -		!wq->idxd->user_submission_safe)
> +	    wq->idxd->hw.version == DEVICE_VERSION_1 &&
> +	    !wq->idxd->user_submission_safe)
>   		return -EINVAL;
>   	/*
>   	 * As per the programming specification, the completion address must be
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 6af493f6ba77..9f0701021af0 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1208,9 +1208,11 @@ static ssize_t op_cap_show_common(struct device *dev, char *buf, unsigned long *
>   
>   		/* On systems where direct user submissions are not safe, we need to clear out
>   		 * the BATCH capability from the capability mask in sysfs since we cannot support
> -		 * that command on such systems.
> +		 * that command on such systems. Narrow the restriction of operations with the
> +		 * BATCH opcode to only DSA version 1 devices.
>   		 */
> -		if (i == DSA_OPCODE_BATCH/64 && !confdev_to_idxd(dev)->user_submission_safe)
> +		if (i == DSA_OPCODE_BATCH/64 && !confdev_to_idxd(dev)->user_submission_safe &&
> +		    confdev_to_idxd(dev)->hw.version == DEVICE_VERSION_1)
>   			clear_bit(DSA_OPCODE_BATCH % 64, &val);
>   
>   		pos += sysfs_emit_at(buf, pos, "%*pb", 64, &val)

Maybe folder the DEVICE_VERSION_1 check into user_submission_safe variable?

This way patch is a bit smaller, a bit faster in run-time,  and easier 
to be extend in case there are other restriction changes in the future?

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 86075cdc4420..80f95cb815c8 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -1258,7 +1258,8 @@ int idxd_pci_probe_alloc(struct idxd_device *idxd, 
struct pci_dev *pdev,
                  idxd->hw.version);

         if (data)
-               idxd->user_submission_safe = data->user_submission_safe;
+               idxd->user_submission_safe = data->user_submission_safe |
+                                            (idxd->hw.version != 
DEVICE_VERSION_1);

Thanks.


-Fenghua