Re: [PATCH v10 12/13] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()

Jason Gunthorpe
2020-11-25T00:00:22Z

On Fri, Sep 18, 2020 at 12:18:52PM +0200, Jean-Philippe Brucker wrote:

> +/* Allocate or get existing MMU notifier for this {domain, mm} pair */
> +static struct arm_smmu_mmu_notifier *
> +arm_smmu_mmu_notifier_get(struct arm_smmu_domain *smmu_domain,
> + struct mm_struct *mm)
> +{
> + int ret;
> + struct arm_smmu_ctx_desc *cd;
> + struct arm_smmu_mmu_notifier *smmu_mn;
> +
> + list_for_each_entry(smmu_mn, &smmu_domain->mmu_notifiers, list) {
> + if (smmu_mn->mn.mm == mm) {
> + refcount_inc(&smmu_mn->refs);
> + return smmu_mn;
> + }
> + }
> +
> + cd = arm_smmu_alloc_shared_cd(mm);
> + if (IS_ERR(cd))
> + return ERR_CAST(cd);
> +
> + smmu_mn = kzalloc(sizeof(*smmu_mn), GFP_KERNEL);
> + if (!smmu_mn) {
> + ret = -ENOMEM;
> + goto err_free_cd;
> + }
> +
> + refcount_set(&smmu_mn->refs, 1);
> + smmu_mn->cd = cd;
> + smmu_mn->domain = smmu_domain;
> + smmu_mn->mn.ops = &arm_smmu_mmu_notifier_ops;
> +
> + ret = mmu_notifier_register(&smmu_mn->mn, mm);
> + if (ret) {
> + kfree(smmu_mn);
> + goto err_free_cd;
> + }

I suppose this hasn't been applied yet, but someone asked me to look
at this series..

Why did you drop the change to mmu_notifier_get here? I'm strongly
trying to discourage static lists matching mm's like smmu_mn is
doing. This is handled by the core code, don't open code it..

Thanks,
Jason