Re: [PATCH 3/6] iommu/vt-d: Make helpers support modifying present pasid entry

[Yi Liu <yi.l.liu@intel.com>]

On 2024/7/15 15:53, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Friday, June 28, 2024 4:56 PM
>>
>> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
>> index b18eebb479de..5d3a12b081a2 100644
>> --- a/drivers/iommu/intel/pasid.c
>> +++ b/drivers/iommu/intel/pasid.c
>> @@ -314,6 +314,9 @@ int intel_pasid_setup_first_level(struct intel_iommu
>> *iommu,
>>   		return -EINVAL;
>>   	}
>>
>> +	/* Clear the old configuration if it already exists */
>> +	intel_pasid_tear_down_entry(iommu, dev, pasid, false, true);
>> +
>>   	spin_lock(&iommu->lock);
>>   	pte = intel_pasid_get_entry(dev, pasid);
>>   	if (!pte) {
> 
> with this change there will be two invocations on
> intel_pasid_tear_down_entry() in the call stack of RID attach:
> 
>    intel_iommu_attach_device()
>      device_block_translation()
>        intel_pasid_tear_down_entry()
>      dmar_domain_attach_device()
>        domain_setup_first_level()
>          intel_pasid_tear_down_entry()
> 
> it's not being a real problem as intel_pasid_tear_down_entry()
> exits early if the pasid entry is non-present, but it will likely cause
> confusion when reading the code.
> 
> What about moving it into intel_iommu_set_dev_pasid() to
> better show the purpose?

I see. will do.

-- 
Regards,
Yi Liu