Re: [PATCH 6/7] iommu/vt-d: Add helper to flush caches for context change

[Baolu Lu]

On 2024/8/15 6:27, Alex Williamson wrote:
> Hi Baolu,

Hi Alex,

> This appears to be non-functional and breaks device assignment...

Yes. This is broken. Thanks for pointing it out.

Perhaps I can fix it by passing domain id to the helper? Something like
below:

diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index 01002ae2a091..b3b295e60626 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -1152,7 +1152,7 @@ void cache_tag_flush_range_np(struct dmar_domain 
*domain, unsigned long start,

 void intel_context_flush_present(struct device_domain_info *info,
 				 struct context_entry *context,
-				 bool affect_domains);
+				 u16 did, bool affect_domains);

 #ifdef CONFIG_INTEL_IOMMU_SVM
 void intel_svm_check(struct intel_iommu *iommu);
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 159da629349c..34006b6e89eb 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1903,6 +1903,7 @@ static void domain_context_clear_one(struct 
device_domain_info *info, u8 bus, u8
 {
 	struct intel_iommu *iommu = info->iommu;
 	struct context_entry *context;
+	u16 did;

 	spin_lock(&iommu->lock);
 	context = iommu_context_addr(iommu, bus, devfn, 0);
@@ -1911,10 +1912,11 @@ static void domain_context_clear_one(struct 
device_domain_info *info, u8 bus, u8
 		return;
 	}

+	did = context_domain_id(context);
 	context_clear_entry(context);
 	__iommu_flush_cache(iommu, context, sizeof(*context));
 	spin_unlock(&iommu->lock);
-	intel_context_flush_present(info, context, true);
+	intel_context_flush_present(info, context, did, true);
 }

 static int domain_setup_first_level(struct intel_iommu *iommu,
@@ -4077,6 +4079,7 @@ static int context_flip_pri(struct 
device_domain_info *info, bool enable)
 	struct intel_iommu *iommu = info->iommu;
 	u8 bus = info->bus, devfn = info->devfn;
 	struct context_entry *context;
+	u16 did;

 	spin_lock(&iommu->lock);
 	if (context_copied(iommu, bus, devfn)) {
@@ -4089,6 +4092,7 @@ static int context_flip_pri(struct 
device_domain_info *info, bool enable)
 		spin_unlock(&iommu->lock);
 		return -ENODEV;
 	}
+	did = context_domain_id(context);

 	if (enable)
 		context_set_sm_pre(context);
@@ -4097,7 +4101,7 @@ static int context_flip_pri(struct 
device_domain_info *info, bool enable)

 	if (!ecap_coherent(iommu->ecap))
 		clflush_cache_range(context, sizeof(*context));
-	intel_context_flush_present(info, context, true);
+	intel_context_flush_present(info, context, did, true);
 	spin_unlock(&iommu->lock);

 	return 0;
diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index 5792c817cefa..b51fc268dc84 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -683,6 +683,7 @@ static void device_pasid_table_teardown(struct 
device *dev, u8 bus, u8 devfn)
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	struct intel_iommu *iommu = info->iommu;
 	struct context_entry *context;
+	u16 did;

 	spin_lock(&iommu->lock);
 	context = iommu_context_addr(iommu, bus, devfn, false);
@@ -691,10 +692,11 @@ static void device_pasid_table_teardown(struct 
device *dev, u8 bus, u8 devfn)
 		return;
 	}

+	did = context_domain_id(context);
 	context_clear_entry(context);
 	__iommu_flush_cache(iommu, context, sizeof(*context));
 	spin_unlock(&iommu->lock);
-	intel_context_flush_present(info, context, false);
+	intel_context_flush_present(info, context, did, false);
 }

 static int pci_pasid_table_teardown(struct pci_dev *pdev, u16 alias, 
void *data)
@@ -885,10 +887,9 @@ static void __context_flush_dev_iotlb(struct 
device_domain_info *info)
  */
 void intel_context_flush_present(struct device_domain_info *info,
 				 struct context_entry *context,
-				 bool flush_domains)
+				 u16 did, bool flush_domains)
 {
 	struct intel_iommu *iommu = info->iommu;
-	u16 did = context_domain_id(context);
 	struct pasid_entry *pte;
 	int i;

Thanks,
baolu