iommu/vt-d: Cleanup intel_context_flush_present()

The intel_context_flush_present() is called in places where either the
scalable mode is disabled, or scalable mode is enabled but all PASID
entries are known to be non-present. In these cases, the flush_domains
path within intel_context_flush_present() will never execute. This dead
code is therefore removed.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Link: https://lore.kernel.org/r/20250228092631.3425464-7-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: LuBaolu

drivers/iommu/intel/iommu.c

@@ -1783,7 +1783,7 @@ static void domain_context_clear_one(struct device_domain_info *info, u8 bus, u8
 	context_clear_entry(context);
 	__iommu_flush_cache(iommu, context, sizeof(*context));
 	spin_unlock(&iommu->lock);
-	intel_context_flush_present(info, context, did, true);
+	intel_context_flush_no_pasid(info, context, did);
 }
 
 int __domain_setup_first_level(struct intel_iommu *iommu,

drivers/iommu/intel/iommu.h

@@ -1286,9 +1286,8 @@ void cache_tag_flush_all(struct dmar_domain *domain);
 void cache_tag_flush_range_np(struct dmar_domain *domain, unsigned long start,
 			      unsigned long end);
 
-void intel_context_flush_present(struct device_domain_info *info,
-				 struct context_entry *context,
-				 u16 did, bool affect_domains);
+void intel_context_flush_no_pasid(struct device_domain_info *info,
+				  struct context_entry *context, u16 did);
 
 int intel_iommu_enable_prq(struct intel_iommu *iommu);
 int intel_iommu_finish_prq(struct intel_iommu *iommu);

drivers/iommu/intel/pasid.c

@@ -932,7 +932,7 @@ static void device_pasid_table_teardown(struct device *dev, u8 bus, u8 devfn)
 	context_clear_entry(context);
 	__iommu_flush_cache(iommu, context, sizeof(*context));
 	spin_unlock(&iommu->lock);
-	intel_context_flush_present(info, context, did, false);
+	intel_context_flush_no_pasid(info, context, did);
 }
 
 static int pci_pasid_table_teardown(struct pci_dev *pdev, u16 alias, void *data)
@@ -1119,17 +1119,15 @@ static void __context_flush_dev_iotlb(struct device_domain_info *info)
 
 /*
  * Cache invalidations after change in a context table entry that was present
- * according to the Spec 6.5.3.3 (Guidance to Software for Invalidations). If
- * IOMMU is in scalable mode and all PASID table entries of the device were
- * non-present, set flush_domains to false. Otherwise, true.
+ * according to the Spec 6.5.3.3 (Guidance to Software for Invalidations).
+ * This helper can only be used when IOMMU is working in the legacy mode or
+ * IOMMU is in scalable mode but all PASID table entries of the device are
+ * non-present.
  */
-void intel_context_flush_present(struct device_domain_info *info,
-				 struct context_entry *context,
-				 u16 did, bool flush_domains)
+void intel_context_flush_no_pasid(struct device_domain_info *info,
+				  struct context_entry *context, u16 did)
 {
 	struct intel_iommu *iommu = info->iommu;
-	struct pasid_entry *pte;
-	int i;
 
 	/*
 	 * Device-selective context-cache invalidation. The Domain-ID field
@@ -1152,30 +1150,5 @@ void intel_context_flush_present(struct device_domain_info *info,
 		return;
 	}
 
-	/*
-	 * For scalable mode:
-	 * - Domain-selective PASID-cache invalidation to affected domains
-	 * - Domain-selective IOTLB invalidation to affected domains
-	 * - Global Device-TLB invalidation to affected functions
-	 */
-	if (flush_domains) {
-		/*
-		 * If the IOMMU is running in scalable mode and there might
-		 * be potential PASID translations, the caller should hold
-		 * the lock to ensure that context changes and cache flushes
-		 * are atomic.
-		 */
-		assert_spin_locked(&iommu->lock);
-		for (i = 0; i < info->pasid_table->max_pasid; i++) {
-			pte = intel_pasid_get_entry(info->dev, i);
-			if (!pte || !pasid_pte_is_present(pte))
-				continue;
-
-			did = pasid_get_domain_id(pte);
-			qi_flush_pasid_cache(iommu, did, QI_PC_ALL_PASIDS, 0);
-			iommu->flush.flush_iotlb(iommu, did, 0, 0, DMA_TLB_DSI_FLUSH);
-		}
-	}
-
 	__context_flush_dev_iotlb(info);
 }