linux-kernel - Re: [PATCH v10 08/12] iommu/sva: Refactoring iommu_sva_bind/unbind

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Message-ID: <Yt5n6JCrigzh3cwh@myrica>
Date:   Mon, 25 Jul 2022 10:52:40 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 08/12] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()

On Mon, Jul 25, 2022 at 05:33:05PM +0800, Baolu Lu wrote:
> Hi Jean,
> 
> On 2022/7/25 15:39, Jean-Philippe Brucker wrote:
> > On Sun, Jul 24, 2022 at 09:48:15PM +0800, Baolu Lu wrote:
> > > /*
> > >   * iommu_detach_device_pasid() - Detach the domain from pasid of device
> > >   * @domain: the iommu domain.
> > >   * @dev: the attached device.
> > >   * @pasid: the pasid of the device.
> > >   *
> > >   * The @domain must have been attached to @pasid of the @dev with
> > >   * iommu_detach_device_pasid().
> > >   */
> > > void iommu_detach_device_pasid(struct iommu_domain *domain, struct device
> > > *dev,
> > > 			       ioasid_t pasid)
> > > {
> > > 	struct iommu_group *group = iommu_group_get(dev);
> > > 	struct group_pasid *param;
> > > 
> > > 	mutex_lock(&group->mutex);
> > > 	domain->ops->set_dev_pasid(group->blocking_domain, dev, pasid);
> > Please also pass the old domain to this detach() function, so that the
> > IOMMU driver doesn't have to keep track of them internally.
> 
> The iommu core provides the interface to retrieve attached domain with a
> {device, pasid} pair. Therefore in the smmuv3 driver, the set_dev_pasid
> could do like this:

Thanks for the example, yes I can do something like this. I maintain that
attach+detach is clearer, but as long as it can be made to work, fine by
me

Thanks,
Jean

> 
> +static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
> +                                     struct device *dev, ioasid_t id)
> +{
> +       int ret = 0;
> +       struct mm_struct *mm;
> +       struct iommu_sva *handle;
> +
> +       /*
> +        * Detach the domain if a blocking domain is set. Check the
> +        * right domain type once the IOMMU driver supports a real
> +        * blocking domain.
> +        */
> +       if (!domain || domain->type == IOMMU_DOMAIN_UNMANAGED) {
> +               struct pasid_iommu *param;
> +
> +               param = iommu_device_pasid_param(dev, id);
> +               if (!param || !param->domain)
> +                       return -EINVAL;
> +               arm_smmu_sva_block_dev_pasid(param->domain, dev, id);
> +
> +               return 0;
> +       }
> +
> +       mm = domain->mm;
> +       mutex_lock(&sva_lock);
> +       handle = __arm_smmu_sva_bind(dev, mm);
> +       if (IS_ERR(handle))
> +               ret = PTR_ERR(handle);
> +       mutex_unlock(&sva_lock);
> +
> +       return ret;
> +}
> 
> The check of "(!domain || domain->type == IOMMU_DOMAIN_UNMANAGED)" looks
> odd, but could get cleaned up after a real blocking domain is added.
> Then, we can simply check "domain->type == IOMMU_DOMAIN_BLOCKING".