[PATCH] iommu: Unify iova_to_phys for identity domains

[Robin Murphy]

On 2021-07-15 02:38, Lu Baolu wrote:
> On 7/15/21 1:28 AM, Robin Murphy wrote:
>> If people are going to insist on calling iommu_iova_to_phys()
>> pointlessly and expecting it to work, we can at least do ourselves a
>> favour by handling those cases in the core code, rather than repeatedly
>> across an inconsistent handful of drivers.
>>
>> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
>> ---
>>   drivers/iommu/amd/io_pgtable.c              | 3 ---
>>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu.c       | 3 ---
>>   drivers/iommu/iommu.c                       | 6 +++++-
>>   4 files changed, 5 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/iommu/amd/io_pgtable.c 
>> b/drivers/iommu/amd/io_pgtable.c
>> index bb0ee5c9fde7..182c93a43efd 100644
>> --- a/drivers/iommu/amd/io_pgtable.c
>> +++ b/drivers/iommu/amd/io_pgtable.c
>> @@ -493,9 +493,6 @@ static phys_addr_t iommu_v1_iova_to_phys(struct 
>> io_pgtable_ops *ops, unsigned lo
>>       unsigned long offset_mask, pte_pgsize;
>>       u64 *pte, __pte;
>> -    if (pgtable->mode == PAGE_MODE_NONE)
>> -        return iova;
>> -
>>       pte = fetch_pte(pgtable, iova, &pte_pgsize);
>>       if (!pte || !IOMMU_PTE_PRESENT(*pte))
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c 
>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 3e87a9cf6da3..c9fdd0d097be 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -2481,9 +2481,6 @@ arm_smmu_iova_to_phys(struct iommu_domain 
>> *domain, dma_addr_t iova)
>>   {
>>       struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
>> -    if (domain->type == IOMMU_DOMAIN_IDENTITY)
>> -        return iova;
>> -
>>       if (!ops)
>>           return 0;
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c 
>> b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> index 0f181f76c31b..0d04eafa3fdb 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> @@ -1317,9 +1317,6 @@ static phys_addr_t arm_smmu_iova_to_phys(struct 
>> iommu_domain *domain,
>>       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>>       struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
>> -    if (domain->type == IOMMU_DOMAIN_IDENTITY)
>> -        return iova;
>> -
>>       if (!ops)
>>           return 0;
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 43a2041d9629..7c16f977b5a6 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -2371,7 +2371,11 @@ EXPORT_SYMBOL_GPL(iommu_detach_group);
>>   phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, 
>> dma_addr_t iova)
>>   {
>> -    if (unlikely(domain->ops->iova_to_phys == NULL))
>> +    if (domain->type == IOMMU_DOMAIN_IDENTITY)
>> +        return iova;
>> +
>> +    if (unlikely(domain->ops->iova_to_phys == NULL) ||
>> +        domain->type == IOMMU_DOMAIN_BLOCKED)
>>           return 0;
> 
> Nit:
> Logically we only needs ops->iova_to_phys for DMA and UNMANAGED domains,
> so it looks better if we have
> 
>      if (domain->type == IOMMU_DOMAIN_BLOCKED ||
>          unlikely(domain->ops->iova_to_phys == NULL))
>          return 0;

Yeah, I put IOMMU_DOMAIN_BLOCKED last as the least likely condition 
since it's really just for completeness - I don't think it's possible to 
see it legitimately used at the moment - but on second look I think 
ops->iova_to_phys == NULL is equally theoretical now, so maybe I could 
be removing that and we just make it mandatory for any new drivers?

> Anyway,
> 
> Reviewed-by: Lu Baolu <baolu.lu at linux.intel.com>

Thanks!

Robin.

> 
> Best regards,
> baolu
> 
>>       return domain->ops->iova_to_phys(domain, iova);
>>