linux-kernel - Re: [PATCH v4 5/7] iommu/vt-d: Make device pasid attachment explicit

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Date:   Mon, 10 Apr 2023 11:14:49 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org
Cc:     baolu.lu@...ux.intel.com, Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>
Subject: Re: [PATCH v4 5/7] iommu/vt-d: Make device pasid attachment explicit

On 4/10/23 10:46 AM, Baolu Lu wrote:
>> @@ -4040,6 +4100,7 @@ static void device_block_translation(struct 
>> device *dev)
>>       spin_lock_irqsave(&info->domain->lock, flags);
>>       list_del(&info->link);
>> +    info->dev_attached = 0;
>>       spin_unlock_irqrestore(&info->domain->lock, flags);
>>       domain_detach_iommu(info->domain, iommu);
>> @@ -4186,7 +4247,7 @@ static int intel_iommu_attach_device(struct 
>> iommu_domain *domain,
>>       if (ret)
>>           return ret;
>> -    return dmar_domain_attach_device(to_dmar_domain(domain), dev);
>> +    return dmar_domain_attach_device_pasid(to_dmar_domain(domain), 
>> dev, PASID_RID2PASID);
>>   }
> 
> For VT-d driver, attach_dev and attach_dev_pasid have different
> meanings. Merging them into one helper may lead to confusion. What do
> you think of the following code? The dmar_domain_attach_device_pasid()
> helper could be reused for attach_dev_pasid path.
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 7c2f4bd33582..09ae62bc3724 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2434,6 +2434,40 @@ static int __init si_domain_init(int hw)
>       return 0;
>   }
> 
> +
> +static int dmar_domain_attach_device_pasid(struct dmar_domain *domain,
> +                       struct intel_iommu *iommu,
> +                       struct device *dev, ioasid_t pasid)
> +{
> +    struct device_pasid_info *dev_pasid;
> +    unsigned long flags;
> +    int ret;
> +
> +    dev_pasid = kzalloc(sizeof(*dev_pasid), GFP_KERNEL);
> +    if (!dev_pasid)
> +        return -ENOMEM;
> +
> +    if (hw_pass_through && domain_type_is_si(domain))
> +        ret = intel_pasid_setup_pass_through(iommu, domain, dev, pasid);
> +    else if (domain->use_first_level)
> +        ret = domain_setup_first_level(iommu, domain, dev, pasid);
> +    else
> +        ret = intel_pasid_setup_second_level(iommu, domain, dev, pasid);
> +
> +    if (ret) {
> +        kfree(dev_pasid);
> +        return ret;
> +    }
> +
> +    dev_pasid->pasid = pasid;
> +    dev_pasid->dev = dev;
> +    spin_lock_irqsave(&domain->lock, flags);
> +    list_add(&dev_pasid->link_domain, &domain->dev_pasids);
> +    spin_unlock_irqrestore(&domain->lock, flags);
> +
> +    return 0;
> +}
> +
>   static int dmar_domain_attach_device(struct dmar_domain *domain,
>                        struct device *dev)
>   {
> @@ -2458,15 +2492,8 @@ static int dmar_domain_attach_device(struct 
> dmar_domain *domain,
>       /* PASID table is mandatory for a PCI device in scalable mode. */
>       if (sm_supported(iommu) && !dev_is_real_dma_subdevice(dev)) {
>           /* Setup the PASID entry for requests without PASID: */
> -        if (hw_pass_through && domain_type_is_si(domain))
> -            ret = intel_pasid_setup_pass_through(iommu, domain,
> -                    dev, PASID_RID2PASID);
> -        else if (domain->use_first_level)
> -            ret = domain_setup_first_level(iommu, domain, dev,
> -                    PASID_RID2PASID);
> -        else
> -            ret = intel_pasid_setup_second_level(iommu, domain,
> -                    dev, PASID_RID2PASID);
> +        ret = dmar_domain_attach_device_pasid(domain, iommu, dev,
> +                              PASID_RID2PASID);
>           if (ret) {
>               dev_err(dev, "Setup RID2PASID failed\n");
>               device_block_translation(dev);

Sorry! I forgot one thing. The dev_pasid data allocated in attach_dev
path should be freed in device_block_translation(). Perhaps we need to
add below change?

@@ -4107,6 +4134,7 @@ static void device_block_translation(struct device 
*dev)
  {
         struct device_domain_info *info = dev_iommu_priv_get(dev);
         struct intel_iommu *iommu = info->iommu;
+       struct device_pasid_info *dev_pasid;
         unsigned long flags;

         iommu_disable_pci_caps(info);
@@ -4118,6 +4146,16 @@ static void device_block_translation(struct 
device *dev)
                         domain_context_clear(info);
         }

+       spin_lock_irqsave(&info->domain->lock, flags);
+       list_for_each_entry(dev_pasid, &domain->dev_pasids, link_domain) {
+               if (dev_pasid->dev != dev || dev_pasid->pasid != RID2PASID)
+                       continue;
+
+               list_del(&dev_pasid->link_domain);
+               kfree(dev_pasid);
+       }
+       spin_unlock_irqrestore(&info->domain->lock, flags);
+
         if (!info->domain)
                 return;

Best regards,
baolu