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Date:   Mon, 25 Sep 2023 14:37:47 +0800
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Subject: Re: [PATCH 6/6] iommu/vt-d: Add domain_alloc_user op
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To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     Baolu Lu <baolu.lu@linux.intel.com>,
        "joro@8bytes.org" <joro@8bytes.org>,
        "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
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        "Duan, Zhenzhong" <zhenzhong.duan@intel.com>,
        "Martins, Joao" <joao.m.martins@oracle.com>
References: <20230919092523.39286-1-yi.l.liu@intel.com>
 <20230919092523.39286-7-yi.l.liu@intel.com>
 <7aa8fd9e-e43d-db68-bdb6-fe4f891255ca@linux.intel.com>
 <20230920130522.GV13733@nvidia.com>
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 <20230920131822.GZ13733@nvidia.com>
From:   Yi Liu <yi.l.liu@intel.com>
In-Reply-To: <20230920131822.GZ13733@nvidia.com>
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On 2023/9/20 21:18, Jason Gunthorpe wrote:
> On Wed, Sep 20, 2023 at 01:10:04PM +0000, Liu, Yi L wrote:
>>> From: Jason Gunthorpe <jgg@nvidia.com>
>>> Sent: Wednesday, September 20, 2023 9:05 PM
>>>
>>> On Wed, Sep 20, 2023 at 01:28:41PM +0800, Baolu Lu wrote:
>>>>>
>>>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>>>> index 5db283c17e0d..491bcde1ff96 100644
>>>>> --- a/drivers/iommu/intel/iommu.c
>>>>> +++ b/drivers/iommu/intel/iommu.c
>>>>> @@ -4074,6 +4074,25 @@ static struct iommu_domain
>>> *intel_iommu_domain_alloc(unsigned type)
>>>>>    	return NULL;
>>>>>    }
>>>>> +static struct iommu_domain *
>>>>> +intel_iommu_domain_alloc_user(struct device *dev, u32 flags)
>>>>> +{
>>>>> +	struct iommu_domain *domain;
>>>>> +	struct intel_iommu *iommu;
>>>>> +
>>>>> +	iommu = device_to_iommu(dev, NULL, NULL);
>>>>> +	if (!iommu)
>>>>> +		return ERR_PTR(-ENODEV);
>>>>> +
>>>>> +	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !ecap_nest(iommu-
>>>> ecap))
>>>>> +		return ERR_PTR(-EOPNOTSUPP);
>>>
>>> There is a check missing for supported flags
>>>
>>>   if (flags & (~IOMMU_HWPT_ALLOC_NEST_PARENT))
>>> 	return ERR_PTR(-EOPNOTSUPP);
>>
>> Well, the iommufd has such check. But I also noticed your another
>> reply to Weijiang. So your preference is to do the flags validation
>> in iommu driver instead of iommufd. Isn't it?
> 
> The core code should check that only kernel known bits are set
> 
> The driver code should check that only driver supported bits are set.
> 
> Today there is only one bit so the checks are the same code.
> 
> Tomorrow when we add a new bit the checks will not be the same

fair enough. I'll have the check in both core and iommu driver.

    if (flags & (~IOMMU_HWPT_ALLOC_NEST_PARENT))
  	return ERR_PTR(-EOPNOTSUPP);


-- 
Regards,
Yi Liu