linux-kernel - Re: [PATCH v2 5/5] iommu/vt-d: Add nested domain support

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Date:   Tue, 14 Mar 2023 09:21:46 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Liu, Jingqi" <jingqi.liu@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        joro@...tes.org, alex.williamson@...hat.com, jgg@...dia.com,
        kevin.tian@...el.com, robin.murphy@....com
Cc:     baolu.lu@...ux.intel.com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v2 5/5] iommu/vt-d: Add nested domain support

On 3/13/23 5:11 PM, Liu, Jingqi wrote:
>> +struct iommu_domain *intel_nested_domain_alloc(struct iommu_domain *s2_domain,
>> +					       const void *user_data)
>> +{
>> +	const struct iommu_hwpt_intel_vtd *vtd = user_data;
>> +	struct dmar_domain *domain;
>> +
> 
> Would it be better to add the following check ?
> 
> 	if (WARN_ON(!user_data))
> 		return NULL;

The iommufd has already done the sanity check. Considering that this
callback is only for iommufd purpose, the individual driver has no need
to check it.

Best regards,
baolu