Re: [PATCH v2 1/8] iommu: Refactor __iommu_domain_alloc()

[Vasant Hegde <vasant.hegde@amd.com>]

Hi Jacob,


On 9/13/2024 9:32 AM, Jacob Pan wrote:
> Hi Vasant,
> 
> On Wed, 11 Sep 2024 10:19:04 +0000
> Vasant Hegde <vasant.hegde@amd.com> wrote:
> 
>> @@ -1962,27 +1978,7 @@ static struct iommu_domain
>> *__iommu_domain_alloc(const struct iommu_ops *ops, if (!domain)
>>  		return ERR_PTR(-ENOMEM);
>>  
>> -	domain->type = type;
>> -	domain->owner = ops;
>> -	/*
>> -	 * If not already set, assume all sizes by default; the
>> driver
>> -	 * may override this later
>> -	 */
>> -	if (!domain->pgsize_bitmap)
>> -		domain->pgsize_bitmap = ops->pgsize_bitmap;
>> -
>> -	if (!domain->ops)
>> -		domain->ops = ops->default_domain_ops;
>> -
>> -	if (iommu_is_dma_domain(domain)) {
>> -		int rc;
>> -
>> -		rc = iommu_get_dma_cookie(domain);
>> -		if (rc) {
>> -			iommu_domain_free(domain);
>> -			return ERR_PTR(rc);
>> -		}
>> -	}
>> +	iommu_domain_init(domain, type, ops);
>>  	return domain;
>>  }
>>  
>> @@ -2965,6 +2961,14 @@ static int iommu_setup_default_domain(struct
>> iommu_group *group, if (group->default_domain == dom)
>>  		return 0;
>>  
>> +	if (iommu_is_dma_domain(dom)) {
>> +		ret = iommu_get_dma_cookie(dom);
>> +		if (ret) {
>> +			iommu_domain_free(dom);
>> +			return ret;
>> +		}
>> +	}
>> +
> nit, if a user changes default domain types via sysfs and the current
> domain is already DMA API type, i.e. DMA to DMA-FQ, I think it causes an
> extra round of iommu_get/put_dma_cookie() compared with doing this in
> allocation time.

DMA -> DMA_FQ will just initialize flush queue and exit. It will not enter
iommu_setup_default_domain(). In case of DMA_FQ -> DMA it will do new domain
allocation. Am I missing something here?


-Vasant