Re: [PATCH v7 10/14] iommu/arm-smmu-v3: Put the SVA mmu notifier in the smmu_domain

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, May 08, 2024 at 03:57:18PM -0300, Jason Gunthorpe wrote:
> This removes all the notifier de-duplication logic in the driver and
> relies on the core code to de-duplicate and allocate only one SVA domain
> per mm per smmu instance. This naturally gives a 1:1 relationship between
> SVA domain and mmu notifier.
> 
> It is a significant simplication of the flow, as we end up with a single
> struct arm_smmu_domain for each MM and the invalidation can then be
> shifted to properly use the masters list like S1/S2 do.
> 
> Remove all of the previous mmu_notifier, bond, shared cd, and cd refcount
> logic entirely.
> 
> The logic here is tightly wound together with the unusued BTM
> support. Since the BTM logic requires holding all the iommu_domains in a
> global ASID xarray it conflicts with the design to have a single SVA
> domain per PASID, as multiple SMMU instances will need to have different
> domains.
> 
> Following patches resolve this by making the ASID xarray per-instance
> instead of global. However, converting the BTM code over to this
> methodology requires many changes.
> 
> Thus, since ARM_SMMU_FEAT_BTM is never enabled, remove the parts of the
> BTM support for ASID sharing that interact with SVA as well.
> 
> A followup series is already working on fully enabling the BTM support,
> that requires iommufd's VIOMMU feature to bring in the KVM's VMID as
> well. It will come with an already written patch to bring back the ASID
> sharing using a per-instance ASID xarray.
> 
> https://lore.kernel.org/linux-iommu/20240208151837.35068-1-shameerali.kolothum.thodi@huawei.com/
> https://lore.kernel.org/linux-iommu/26-v6-228e7adf25eb+4155-smmuv3_newapi_p2_jgg@nvidia.com/
> 
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>

>  static void arm_smmu_mmu_notifier_free(struct mmu_notifier *mn)
>  {
> -	kfree(mn_to_smmu(mn));
> +	struct arm_smmu_domain *smmu_domain =
> +		container_of(mn, struct arm_smmu_domain, mmu_notifier);
> +
> +	kfree(smmu_domain);

Would it be cleaner to refactor mn_to_smmu to mn_to_smmu_domain?

Otherwise, would it feel simpler by just
	kfree(container_of(mn, struct arm_smmu_domain, mmu_notifier));

Thanks
Nicolin