Re: [PATCH v3 1/4] iommu: Check IOMMU_DEV_FEAT_AUX feature in aux api's

Lu Baolu
2020-07-30T01:51:53Z

Hi Alex,

On 7/30/20 4:03 AM, Alex Williamson wrote:
> On Tue, 14 Jul 2020 13:57:00 +0800
> Lu Baolu <baolu.lu@linux.intel.com> wrote:
>
>> The iommu aux-domain api's work only when IOMMU_DEV_FEAT_AUX is enabled
>> for the device. Add this check to avoid misuse.
>
> Shouldn't this really be the IOMMU driver's responsibility to test? If
> nothing else, iommu_dev_feature_enabled() needs to get the iommu_ops
> from dev->bus->iommu_ops, which is presumably the same iommu_ops we're
> then calling from domain->ops to attach/detach the device, so it'd be
> more efficient for the IOMMU driver to error on devices that don't
> support aux. Thanks,

Fair enough. The vendor iommu driver always knows the status of aux-
domain support. So this check is duplicated. I will drop this patch.

Best regards,
baolu

>
> Alex
>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/iommu.c | 16 +++++++++-------
>> 1 file changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 1ed1e14a1f0c..e1fdd3531d65 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -2725,11 +2725,13 @@ EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
>> */
>> int iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev)
>> {
>> - int ret = -ENODEV;
>> + int ret;
>>
>> - if (domain->ops->aux_attach_dev)
>> - ret = domain->ops->aux_attach_dev(domain, dev);
>> + if (!iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX) ||
>> + !domain->ops->aux_attach_dev)
>> + return -ENODEV;
>>
>> + ret = domain->ops->aux_attach_dev(domain, dev);
>> if (!ret)
>> trace_attach_device_to_domain(dev);
>>
>> @@ -2748,12 +2750,12 @@ EXPORT_SYMBOL_GPL(iommu_aux_detach_device);
>>
>> int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
>> {
>> - int ret = -ENODEV;
>> + if (!iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX) ||
>> + !domain->ops->aux_get_pasid)
>> + return -ENODEV;
>>
>> - if (domain->ops->aux_get_pasid)
>> - ret = domain->ops->aux_get_pasid(domain, dev);
>> + return domain->ops->aux_get_pasid(domain, dev);
>>
>> - return ret;
>> }
>> EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
>>