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Message-ID: <3e75f9de-4c67-93aa-9fb4-28da9849dd48@linux.intel.com>
Date:   Wed, 31 May 2023 11:26:55 +0800
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Cc:     baolu.lu@linux.intel.com, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] iommu/vt-d: Use BUG_ON to check NULL value of 'table'
Content-Language: en-US
To:     Yanfei Xu <yanfei.xu@intel.com>, dwmw2@infradead.org,
        joro@8bytes.org, will@kernel.org, robin.murphy@arm.com
References: <20230530092503.152926-1-yanfei.xu@intel.com>
 <20230530092503.152926-3-yanfei.xu@intel.com>
From:   Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <20230530092503.152926-3-yanfei.xu@intel.com>
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On 5/30/23 5:25 PM, Yanfei Xu wrote:
> Checking NULL value of 'table' variable deserves a BUG_ON as the
> following code will trigger a crash by dereferencing the NULL
> 'table' pointer. Crash in advance with BUG_ON to avoid WARN_ON
> plus NULL pointer dereferencing can simplify the crash log.
> 
> Signed-off-by: Yanfei Xu<yanfei.xu@intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index e98f1b122b49..8aa3bfdb7f95 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1944,7 +1944,7 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
>   	if (sm_supported(iommu)) {
>   		unsigned long pds;
>   
> -		WARN_ON(!table);
> +		BUG_ON(!table);

BUG_ON() is not recommended. Perhaps,

		if (!table)
			-ENODEV;

?

Best regards,
baolu