linux-kernel - Re: [PATCH] iommu/amd: Drop incorrect NULL check for iommu in alloc_irq

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Message-ID: <f6xrnx56thysevryr35bywkthidt3zvxb2zt4ry5ttp5jc4vfp@5ibfyv3672bg>
Date: Wed, 24 Dec 2025 13:43:28 +0000
From: Ankit Soni <Ankit.Soni@....com>
To: Rakuram Eswaran <rakuram.e96@...il.com>
CC: <joro@...tes.org>, <will@...nel.org>, <suravee.suthikulpanit@....com>,
	<robin.murphy@....com>, <iommu@...ts.linux.dev>, <dan.carpenter@...aro.org>,
	<lkp@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/amd: Drop incorrect NULL check for iommu in
 alloc_irq_table()

On Mon, Dec 22, 2025 at 10:40:08PM +0530, Rakuram Eswaran wrote:
> alloc_irq_table() contains a conditional check for a NULL iommu pointer
> when computing the NUMA node, but the function dereferences iommu
> in multiple places afterwards.
> 
> All callers ensure that a valid iommu pointer is passed in, and a NULL
> iommu is not expected by the current callers. Remove the incorrect
> NULL check to make the assumptions consistent and address the Smatch
> warning.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/r/202512191724.meqJENXe-lkp@intel.com/
> Signed-off-by: Rakuram Eswaran <rakuram.e96@...il.com>

Looks good to me.
Reviewed-by: Ankit Soni <Ankit.Soni@....com>

> ---
> Testing note:
> Compile tested only.
> 
> Build and Analysis:
> This patch was compiled against the configuration file reported by
> 0day CI in the above link (config: x86_64-randconfig-r073-20251215)
> using gcc version 15.2.0 (Ubuntu 15.2.0-4ubuntu4).
> 
> Static analysis was performed with Smatch to ensure the reported warning
> no longer reproduces after applying this fix.
> 
> Command using for Smatch testing:
> ~/project/smatch/smatch_scripts/kchecker ./drivers/iommu/amd/iommu.c
> 
>  drivers/iommu/amd/iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 075125f0f52b..611e3ccc93d1 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -3240,7 +3240,7 @@ static struct irq_remap_table *alloc_irq_table(struct amd_iommu *iommu,
>  	struct irq_remap_table *new_table = NULL;
>  	struct amd_iommu_pci_seg *pci_seg;
>  	unsigned long flags;
> -	int nid = iommu && iommu->dev ? dev_to_node(&iommu->dev->dev) : NUMA_NO_NODE;
> +	int nid = iommu->dev ? dev_to_node(&iommu->dev->dev) : NUMA_NO_NODE;
>  	u16 alias;
>  
>  	spin_lock_irqsave(&iommu_table_lock, flags);
> -- 
> 2.51.0
>