Re: [PATCH v4 14/14] iommu/arm-smmu-v3: Report events that belong to devices attached to vIOMMU

[Nicolin Chen <nicolinc@nvidia.com>]

On Tue, Jan 07, 2025 at 01:54:00PM +0800, Baolu Lu wrote:
> On 1/7/25 12:36, Nicolin Chen wrote:
> > +static bool arm_vsmmu_supports_veventq(unsigned int type)
> > +{
> > +	return type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3;
> 
> Do you need to check the hardware capabilities before reporting this? I
> am not familiar with the ARM architecture, but typically it's better to
> make it like this,
> 
> static bool arm_vsmmu_supports_veventq(struct iommufd_viommu *viommu,
>                                        enum iommu_veventq_type type)
> {
> 	if (type != IOMMU_VEVENTQ_TYPE_ARM_SMMUV3)
> 		return false;
> 
> 	if (hardware_not_capable(viommu))
> 		return false;

I think the ARM version of viommu_alloc op has already implemented
enough capability checks and rejected any of hardware_not_capable.
So, viommu shouldn't be a thing that the driver could actually use
to call this helper :)

Thanks
Nicolin