iommu/vt-d: Add helper to flush caches for context change

This helper is used to flush the related caches following a change in a
context table entry that was previously present. The VT-d specification
provides guidance for such invalidations in section 6.5.3.3.

This helper replaces the existing open code in the code paths where a
present context entry is being torn down.
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240701112317.94022-2-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20240702130839.108139-7-baolu.lu@linux.intel.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/iommu/intel/iommu.c

@@ -1359,21 +1359,6 @@ static void iommu_disable_pci_caps(struct device_domain_info *info)
 	}
 }
 
-static void __iommu_flush_dev_iotlb(struct device_domain_info *info,
-				    u64 addr, unsigned int mask)
-{
-	u16 sid, qdep;
-
-	if (!info || !info->ats_enabled)
-		return;
-
-	sid = info->bus << 8 | info->devfn;
-	qdep = info->ats_qdep;
-	qi_flush_dev_iotlb(info->iommu, sid, info->pfsid,
-			   qdep, addr, mask);
-	quirk_extra_dev_tlb_flush(info, addr, mask, IOMMU_NO_PASID, qdep);
-}
-
 static void intel_flush_iotlb_all(struct iommu_domain *domain)
 {
 	cache_tag_flush_all(to_dmar_domain(domain));
@@ -1959,7 +1944,6 @@ 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_old;
 
 	spin_lock(&iommu->lock);
 	context = iommu_context_addr(iommu, bus, devfn, 0);
@@ -1968,24 +1952,10 @@ static void domain_context_clear_one(struct device_domain_info *info, u8 bus, u8
 		return;
 	}
 
-	did_old = context_domain_id(context);
-
 	context_clear_entry(context);
 	__iommu_flush_cache(iommu, context, sizeof(*context));
 	spin_unlock(&iommu->lock);
-	iommu->flush.flush_context(iommu,
-				   did_old,
-				   (((u16)bus) << 8) | devfn,
-				   DMA_CCMD_MASK_NOBIT,
-				   DMA_CCMD_DEVICE_INVL);
-
-	iommu->flush.flush_iotlb(iommu,
-				 did_old,
-				 0,
-				 0,
-				 DMA_TLB_DSI_FLUSH);
-
-	__iommu_flush_dev_iotlb(info, 0, MAX_AGAW_PFN_WIDTH);
+	intel_context_flush_present(info, context, true);
 }
 
 static int domain_setup_first_level(struct intel_iommu *iommu,

drivers/iommu/intel/iommu.h

@@ -1143,6 +1143,10 @@ 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,
+				 bool affect_domains);
+
 #ifdef CONFIG_INTEL_IOMMU_SVM
 void intel_svm_check(struct intel_iommu *iommu);
 int intel_svm_enable_prq(struct intel_iommu *iommu);

drivers/iommu/intel/pasid.c

@@ -694,25 +694,7 @@ 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);
-
-	/*
-	 * Cache invalidation for changes to a scalable-mode context table
-	 * entry.
-	 *
-	 * Section 6.5.3.3 of the VT-d spec:
-	 * - Device-selective context-cache invalidation;
-	 * - Domain-selective PASID-cache invalidation to affected domains
-	 *   (can be skipped if all PASID entries were not-present);
-	 * - Domain-selective IOTLB invalidation to affected domains;
-	 * - Global Device-TLB invalidation to affected functions.
-	 *
-	 * The iommu has been parked in the blocking state. All domains have
-	 * been detached from the device or PASID. The PASID and IOTLB caches
-	 * have been invalidated during the domain detach path.
-	 */
-	iommu->flush.flush_context(iommu, 0, PCI_DEVID(bus, devfn),
-				   DMA_CCMD_MASK_NOBIT, DMA_CCMD_DEVICE_INVL);
-	devtlb_invalidation_with_pasid(iommu, dev, IOMMU_NO_PASID);
+	intel_context_flush_present(info, context, false);
 }
 
 static int pci_pasid_table_teardown(struct pci_dev *pdev, u16 alias, void *data)
@@ -874,3 +856,89 @@ int intel_pasid_setup_sm_context(struct device *dev)
 
 	return pci_for_each_dma_alias(to_pci_dev(dev), pci_pasid_table_setup, dev);
 }
+
+/*
+ * Global Device-TLB invalidation following changes in a context entry which
+ * was present.
+ */
+static void __context_flush_dev_iotlb(struct device_domain_info *info)
+{
+	if (!info->ats_enabled)
+		return;
+
+	qi_flush_dev_iotlb(info->iommu, PCI_DEVID(info->bus, info->devfn),
+			   info->pfsid, info->ats_qdep, 0, MAX_AGAW_PFN_WIDTH);
+
+	/*
+	 * There is no guarantee that the device DMA is stopped when it reaches
+	 * here. Therefore, always attempt the extra device TLB invalidation
+	 * quirk. The impact on performance is acceptable since this is not a
+	 * performance-critical path.
+	 */
+	quirk_extra_dev_tlb_flush(info, 0, MAX_AGAW_PFN_WIDTH, IOMMU_NO_PASID,
+				  info->ats_qdep);
+}
+
+/*
+ * 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.
+ */
+void intel_context_flush_present(struct device_domain_info *info,
+				 struct context_entry *context,
+				 bool flush_domains)
+{
+	struct intel_iommu *iommu = info->iommu;
+	u16 did = context_domain_id(context);
+	struct pasid_entry *pte;
+	int i;
+
+	/*
+	 * Device-selective context-cache invalidation. The Domain-ID field
+	 * of the Context-cache Invalidate Descriptor is ignored by hardware
+	 * when operating in scalable mode. Therefore the @did value doesn't
+	 * matter in scalable mode.
+	 */
+	iommu->flush.flush_context(iommu, did, PCI_DEVID(info->bus, info->devfn),
+				   DMA_CCMD_MASK_NOBIT, DMA_CCMD_DEVICE_INVL);
+
+	/*
+	 * For legacy mode:
+	 * - Domain-selective IOTLB invalidation
+	 * - Global Device-TLB invalidation to all affected functions
+	 */
+	if (!sm_supported(iommu)) {
+		iommu->flush.flush_iotlb(iommu, did, 0, 0, DMA_TLB_DSI_FLUSH);
+		__context_flush_dev_iotlb(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);
+}