linux-kernel - Re: [PATCH v4 12/13] iommu/arm-smmu-v3-sva: Remove arm_smmu

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Date:   Thu, 13 Jul 2023 16:41:45 +0800
From:   Michael Shavit <mshavit@...gle.com>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>
Cc:     jean-philippe@...aro.org, nicolinc@...dia.com, jgg@...dia.com,
        baolu.lu@...ux.intel.com, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 12/13] iommu/arm-smmu-v3-sva: Remove arm_smmu_bond

> On Wed, Jun 21, 2023 at 2:44 PM Michael Shavit <mshavit@...gle.com> wrote:
> @@ -545,23 +534,12 @@ void arm_smmu_sva_notifier_synchronize(void)
>  void arm_smmu_sva_remove_dev_pasid(struct iommu_domain *domain,
>                                    struct device *dev, ioasid_t id)
>  {
> -       struct mm_struct *mm = domain->mm;
> -       struct arm_smmu_bond *bond = NULL, *t;
> +       struct arm_smmu_sva_domain *sva_domain = to_sva_domain(domain);
>         struct arm_smmu_master *master = dev_iommu_priv_get(dev);
>
>         mutex_lock(&sva_lock);
> -       list_for_each_entry(t, &master->bonds, list) {
> -               if (t->mm == mm) {
> -                       bond = t;
> -                       break;
> -               }
> -       }
> -
> -       if (!WARN_ON(!bond)) {
> -               list_del(&bond->list);
> -               arm_smmu_mmu_notifier_put(bond->smmu_mn);
> -               kfree(bond);
> -       }
> +       master->nr_attached_sva_domains -= 1;
> +       arm_smmu_mmu_notifier_put(sva_domain->smmu_mn);
>         mutex_unlock(&sva_lock);
>  }

I've encountered a bug with this change while working on a follow-up
series. arm_smmu_sva_remove_dev_pasid() is called on the domain if
arm_smmu_sva_set_dev_pasid failed. Removing the WARN_ON(!bond)
condition removed a protection against that scenario. I have a fix for
this change that I'll push into a v5 of the series.