linux-kernel - Re: [PATCH v2 2/5] iommu: Introduce mm_get

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Date:   Thu, 31 Aug 2023 13:14:20 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Tina Zhang <tina.zhang@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Michael Shavit <mshavit@...gle.com>
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] iommu: Introduce mm_get_pasid() helper function

On 2023/8/27 16:43, Tina Zhang wrote:
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index e95b339e9cdc0..e6377cff6a935 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -306,13 +306,13 @@ static int intel_svm_bind_mm(struct intel_iommu *iommu, struct device *dev,
>   	unsigned long sflags;
>   	int ret = 0;
>   
> -	svm = pasid_private_find(mm->pasid);
> +	svm = pasid_private_find(mm_get_pasid(mm));
>   	if (!svm) {
>   		svm = kzalloc(sizeof(*svm), GFP_KERNEL);
>   		if (!svm)
>   			return -ENOMEM;
>   
> -		svm->pasid = mm->pasid;
> +		svm->pasid = mm_get_pasid(mm);
>   		svm->mm = mm;
>   		INIT_LIST_HEAD_RCU(&svm->devs);
>   
> @@ -350,7 +350,7 @@ static int intel_svm_bind_mm(struct intel_iommu *iommu, struct device *dev,
>   
>   	/* Setup the pasid table: */
>   	sflags = cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
> -	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm->pasid,
> +	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm_get_pasid(mm),
>   					    FLPT_DEFAULT_DID, sflags);
>   	if (ret)
>   		goto free_sdev;
> @@ -364,7 +364,7 @@ static int intel_svm_bind_mm(struct intel_iommu *iommu, struct device *dev,
>   free_svm:
>   	if (list_empty(&svm->devs)) {
>   		mmu_notifier_unregister(&svm->notifier, mm);
> -		pasid_private_remove(mm->pasid);
> +		pasid_private_remove(mm_get_pasid(mm));
>   		kfree(svm);
>   	}

There is no need to use mm_get_pasid(mm) in the set_dev_pasid path. The
pasid has already passed as a parameter. Perhaps, pass domain and pasid
to intel_svm_bind_mm(), or simply merge intel_svm_bind_mm() to
intel_svm_set_dev_pasid()?

Something like below?

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 8f6d68006ab6..de490b3409cc 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -298,21 +298,22 @@ static int pasid_to_svm_sdev(struct device *dev, 
unsigned int pasid,
  }

  static int intel_svm_bind_mm(struct intel_iommu *iommu, struct device 
*dev,
-			     struct mm_struct *mm)
+			     struct iommu_domain *domain, ioasid_t pasid)
  {
  	struct device_domain_info *info = dev_iommu_priv_get(dev);
+	struct mm_struct *mm = domain->mm;
  	struct intel_svm_dev *sdev;
  	struct intel_svm *svm;
  	unsigned long sflags;
  	int ret = 0;

-	svm = pasid_private_find(mm->pasid);
+	svm = pasid_private_find(pasid);
  	if (!svm) {
  		svm = kzalloc(sizeof(*svm), GFP_KERNEL);
  		if (!svm)
  			return -ENOMEM;

-		svm->pasid = mm->pasid;
+		svm->pasid = pasid;
  		svm->mm = mm;
  		INIT_LIST_HEAD_RCU(&svm->devs);

@@ -350,7 +351,7 @@ static int intel_svm_bind_mm(struct intel_iommu 
*iommu, struct device *dev,

  	/* Setup the pasid table: */
  	sflags = cpu_feature_enabled(X86_FEATURE_LA57) ? PASID_FLAG_FL5LP : 0;
-	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, mm->pasid,
+	ret = intel_pasid_setup_first_level(iommu, dev, mm->pgd, pasid,
  					    FLPT_DEFAULT_DID, sflags);
  	if (ret)
  		goto free_sdev;
@@ -364,7 +365,7 @@ static int intel_svm_bind_mm(struct intel_iommu 
*iommu, struct device *dev,
  free_svm:
  	if (list_empty(&svm->devs)) {
  		mmu_notifier_unregister(&svm->notifier, mm);
-		pasid_private_remove(mm->pasid);
+		pasid_private_remove(pasid);
  		kfree(svm);
  	}

@@ -839,11 +840,10 @@ static int intel_svm_set_dev_pasid(struct 
iommu_domain *domain,
  {
  	struct device_domain_info *info = dev_iommu_priv_get(dev);
  	struct intel_iommu *iommu = info->iommu;
-	struct mm_struct *mm = domain->mm;
  	int ret;

  	mutex_lock(&pasid_mutex);
-	ret = intel_svm_bind_mm(iommu, dev, mm);
+	ret = intel_svm_bind_mm(iommu, dev, domain, pasid);
  	mutex_unlock(&pasid_mutex);

  	return ret;

Best regards,
baolu