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

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Date:   Mon, 25 Jul 2022 17:33:05 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, 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()

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:

+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".

> In addition to clearing contexts, detach() also needs to invalidate TLBs,
> and for that the SMMU driver needs to know the old ASID (!= PASID) that
> was used by the context descriptor.

Best regards,
baolu