linux-kernel - [RFC PATCH 12/12] iommu/vt-d: Remove superfluous IOMMU IOTLB invalidations

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Date:   Tue, 17 Oct 2023 11:20:45 +0800
From:   Tina Zhang <tina.zhang@...el.com>
To:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>,
        Tina Zhang <tina.zhang@...el.com>
Subject: [RFC PATCH 12/12] iommu/vt-d: Remove superfluous IOMMU IOTLB invalidations

Devices behind different IOMMUs can be bound to one sva domain. When a
range of a sva domain address is being invalidated, vt-d driver needs to
issue IOMMU IOTLB and Dev-IOTLB invalidation commands to ask IOMMU
hardware and related devices to invalidate their caches.

The current logic issues both IOTLB invalidation command and device-TLB
command per device, which leads to superfluous IOTLB invalidation (e.g.,
if there are four devices behind a IOMMU are attached to one sva domain.
In the current logic, during handing intel_invalidate_range(), four IOTLB
invalidation commands and four Dev-IOTLB invalidation commands will be
issued. However, only one IOTLB invalidation command and four Dev-IOTLB
invalidation command are necessary.), and therefore impacts run-time
performance.

The patch removes the redundant IOMMU IOTLB invalidations by allowing
issuing IOMMU IOTLB invalidation command per iommu instead of per device.

Signed-off-by: Tina Zhang <tina.zhang@...el.com>
---
 drivers/iommu/intel/svm.c | 56 +++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 29 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index c9a703935908..f684b92a1241 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -135,32 +135,41 @@ void intel_svm_check(struct intel_iommu *iommu)
 	iommu->flags |= VTD_FLAG_SVM_CAPABLE;
 }
 
-static void __flush_svm_range_dev(struct dmar_domain *domain,
-				  struct dev_pasid_info *dev_pasid,
+static void __flush_svm_range(struct iommu_domain *domain,
 				  unsigned long address,
 				  unsigned long pages, int ih)
 {
-	struct device_domain_info *info = dev_iommu_priv_get(dev_pasid->dev);
-	struct intel_iommu *iommu = dev_to_intel_iommu(dev_pasid->dev);
-	u32 pasid = mm_get_enqcmd_pasid(domain->domain.mm);
+	u32 pasid = mm_get_enqcmd_pasid(domain->mm);
+	struct device_domain_info *dev_info;
+	struct iommu_domain_info *iommu_info;
+	struct dev_pasid_info *dev_pasid;
+	struct intel_iommu *iommu;
+	unsigned long idx;
 
 	if (WARN_ON(!pages))
 		return;
 
-	qi_flush_piotlb(iommu, FLPT_DEFAULT_DID, pasid, address, pages, ih);
-	if (info->ats_enabled) {
-		qi_flush_dev_iotlb_pasid(iommu, dev_pasid->sid, info->pfsid,
-					 pasid, dev_pasid->qdep, address,
-					 order_base_2(pages));
-		quirk_extra_dev_tlb_flush(info, address, order_base_2(pages),
-					  pasid, dev_pasid->qdep);
+	rcu_read_lock();
+	xa_for_each(&to_dmar_domain(domain)->iommu_array, idx, iommu_info)
+		qi_flush_piotlb(iommu_info->iommu, FLPT_DEFAULT_DID,
+				pasid, address, pages, ih);
+
+	list_for_each_entry_rcu(dev_pasid, &to_dmar_domain(domain)->dev_pasids, link_domain) {
+		dev_info = dev_iommu_priv_get(dev_pasid->dev);
+		iommu = dev_to_intel_iommu(dev_pasid->dev);
+		if (dev_info->ats_enabled) {
+			qi_flush_dev_iotlb_pasid(iommu, dev_pasid->sid, dev_info->pfsid,
+						 pasid, dev_pasid->qdep, address,
+						 order_base_2(pages));
+			quirk_extra_dev_tlb_flush(dev_info, address, order_base_2(pages),
+						  pasid, dev_pasid->qdep);
+		}
 	}
+	rcu_read_unlock();
 }
 
-static void intel_flush_svm_range_dev(struct dmar_domain *domain,
-				      struct dev_pasid_info *dev_pasid,
-				      unsigned long address,
-				      unsigned long pages, int ih)
+static void intel_flush_svm_range(struct iommu_domain *domain, unsigned long address,
+				unsigned long pages, int ih)
 {
 	unsigned long shift = ilog2(__roundup_pow_of_two(pages));
 	unsigned long align = (1ULL << (VTD_PAGE_SHIFT + shift));
@@ -168,22 +177,11 @@ static void intel_flush_svm_range_dev(struct dmar_domain *domain,
 	unsigned long end = ALIGN(address + (pages << VTD_PAGE_SHIFT), align);
 
 	while (start < end) {
-		__flush_svm_range_dev(domain, dev_pasid, start, align >> VTD_PAGE_SHIFT, ih);
+		__flush_svm_range(domain, start, align >> VTD_PAGE_SHIFT, ih);
 		start += align;
 	}
 }
 
-static void intel_flush_svm_range(struct dmar_domain *domain, unsigned long address,
-				unsigned long pages, int ih)
-{
-	struct dev_pasid_info *dev_pasid;
-
-	rcu_read_lock();
-	list_for_each_entry_rcu(dev_pasid, &domain->dev_pasids, link_domain)
-		intel_flush_svm_range_dev(domain, dev_pasid, address, pages, ih);
-	rcu_read_unlock();
-}
-
 /* Pages have been freed at this point */
 static void intel_arch_invalidate_secondary_tlbs(struct mmu_notifier *mn,
 					struct mm_struct *mm,
@@ -191,7 +189,7 @@ static void intel_arch_invalidate_secondary_tlbs(struct mmu_notifier *mn,
 {
 	struct iommu_domain *domain = container_of(mn, struct iommu_domain, notifier);
 
-	intel_flush_svm_range(to_dmar_domain(domain), start,
+	intel_flush_svm_range(domain, start,
 			      (end - start + PAGE_SIZE - 1) >> VTD_PAGE_SHIFT, 0);
 }
 
-- 
2.39.3