netdev - Re: [iwl-next 6/6] idpf: implement get LAN MMIO memory regions

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Message-ID: <20250528104407.GB365796@horms.kernel.org>
Date: Wed, 28 May 2025 11:44:07 +0100
From: Simon Horman <horms@...nel.org>
To: Tatyana Nikolova <tatyana.e.nikolova@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, jgg@...dia.com, leon@...nel.org,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org, kuba@...nel.org,
	anthony.l.nguyen@...el.com, Joshua Hay <joshua.a.hay@...el.com>
Subject: Re: [iwl-next 6/6] idpf: implement get LAN MMIO memory regions

On Fri, May 23, 2025 at 12:04:35PM -0500, Tatyana Nikolova wrote:
> From: Joshua Hay <joshua.a.hay@...el.com>
> 
> The RDMA driver needs to map its own MMIO regions for the sake of
> performance, meaning the IDPF needs to avoid mapping portions of the BAR
> space. However, the IDPF cannot assume where these are and must avoid
> mapping hard coded regions as much as possible.
> 
> The IDPF maps the bare minimum to load and communicate with the
> control plane, i.e., the mailbox registers and the reset state
> registers. Because of how and when mailbox reigster offsets are
> initialized, it is easier to adjust the existing defines to be relative
> to the mailbox region starting address. Use a specific mailbox register
> write function that uses these relative offsets. The reset state
> register addresses are calculated the same way as for other registers,
> described below.
> 
> The IDPF then calls a new virtchnl op to fetch a list of MMIO regions
> that it should map. The addresses for the registers in these regions are
> calculated by determining what region the register resides in, adjusting
> the offset to be relative to that region, and then adding the
> register's offset to that region's mapped address.
> 
> If the new virtchnl op is not supported, the IDPF will fallback to
> mapping the whole bar. However, it will still map them as separate
> regions outside the mailbox and reset state registers. This way we can
> use the same logic in both cases to access the MMIO space.
> 
> Reviewed-by: Madhu Chittim <madhu.chittim@...el.com>
> Signed-off-by: Joshua Hay <joshua.a.hay@...el.com>
> Signed-off-by: Tatyana Nikolova <tatyana.e.nikolova@...el.com>

...

> diff --git a/drivers/net/ethernet/intel/idpf/idpf_idc.c b/drivers/net/ethernet/intel/idpf/idpf_idc.c

...

> @@ -447,12 +469,15 @@ int idpf_idc_init_aux_core_dev(struct idpf_adapter *adapter,
>   */
>  void idpf_idc_deinit_core_aux_device(struct iidc_rdma_core_dev_info *cdev_info)
>  {
> +	struct iidc_rdma_priv_dev_info *privd = cdev_info->iidc_priv;
> +

Hi Joshua, Tatyana, all,

On the line below it is assumed that cdev_info may be NULL.
But on the line above cdev_info is unconditionally dereferenced.
This doesn't seem consistent.

Flagged by Smatch.

>  	if (!cdev_info)
>  		return;
>  
>  	idpf_unplug_aux_dev(cdev_info->adev);
>  
> -	kfree(cdev_info->iidc_priv);
> +	kfree(privd->mapped_mem_regions);
> +	kfree(privd);
>  	kfree(cdev_info);
>  }
>  

...