Re: [PATCH 2/2] ARM: SMMU: return NULL on error in arm_smmu_iova_to_phys

Antonios Motakis
2013-10-14T15:17:53Z

On Mon, Oct 14, 2013 at 2:48 PM, Will Deacon <will.deacon@arm.com> wrote:
> On Fri, Oct 11, 2013 at 02:24:47PM +0100, Antonios Motakis wrote:
>> The return value of arm_smmu_iova_to_phys is directly passed to the
>> user of the IOMMU API via iommu_iova_to_phys; however the ARM SMMU
>> driver returns -EINVAL on error, which is not consistent with the
>> rest of the drivers implementing the IOMMU API. VFIO also relies on
>> the call returning NULL when a page has not been mapped already.
>>
>> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
>> ---
>> drivers/iommu/arm-smmu.c | 5 +----
>> 1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index 8b71332..fe81b20 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -1480,10 +1480,7 @@ static phys_addr_t arm_smmu_iova_to_phys(struct iommu_domain *domain,
>>
>> err_unlock:
>> spin_unlock(&smmu_domain->lock);
>> - dev_warn(smmu->dev,
>> - "invalid (corrupt?) page tables detected for iova 0x%llx\n",
>> - (unsigned long long)iova);
>> - return -EINVAL;
>> + return NULL;
>
> Why are you removing the warning message?

VFIO will exercise this code path every time when mapping DMA memory.
This is normal and VFIO *expects* the function to fail - it is only if
the function succeeds that VFIO needs to back down from the DMA
mapping and fail.

This means that there would be a warning every time a VFIO user maps
some memory for DMA use, even though nothing went wrong.

>
> Will