linux-kernel - [PATCH v3 4/6] iommu: Factor iommu_iotlb_gather_is

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Date:   Mon,  7 Jun 2021 11:25:39 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Nadav Amit <namit@...are.com>, Will Deacon <will@...nel.org>,
        Jiajun Cao <caojiajun@...are.com>,
        Robin Murphy <robin.murphy@....com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/6] iommu: Factor iommu_iotlb_gather_is_disjoint() out

From: Nadav Amit <namit@...are.com>

Refactor iommu_iotlb_gather_add_page() and factor out the logic that
detects whether IOTLB gather range and a new range are disjoint. To be
used by the next patch that implements different gathering logic for
AMD.

Cc: Joerg Roedel <joro@...tes.org>
Cc: Will Deacon <will@...nel.org>
Cc: Jiajun Cao <caojiajun@...are.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: iommu@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org>
Signed-off-by: Nadav Amit <namit@...are.com>
---
 include/linux/iommu.h | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index f254c62f3720..b5a2bfc68fb0 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -497,6 +497,28 @@ static inline void iommu_iotlb_sync(struct iommu_domain *domain,
 	iommu_iotlb_gather_init(iotlb_gather);
 }
 
+/**
+ * iommu_iotlb_gather_is_disjoint - Checks whether a new range is disjoint
+ *
+ * @gather: TLB gather data
+ * @iova: start of page to invalidate
+ * @size: size of page to invalidate
+ *
+ * Helper for IOMMU drivers to check whether a new range is and the gathered
+ * range are disjoint. For many IOMMUs, flushing the IOMMU in this case is
+ * better than merging the two, which might lead to unnecessary invalidations.
+ */
+static inline
+bool iommu_iotlb_gather_is_disjoint(struct iommu_iotlb_gather *gather,
+				    unsigned long iova, size_t size)
+{
+	unsigned long start = iova, end = start + size - 1;
+
+	return gather->end != 0 &&
+		(end + 1 < gather->start || start > gather->end + 1);
+}
+
+
 /**
  * iommu_iotlb_gather_add_range - Gather for address-based TLB invalidation
  * @gather: TLB gather data
@@ -533,20 +555,16 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 					       struct iommu_iotlb_gather *gather,
 					       unsigned long iova, size_t size)
 {
-	unsigned long start = iova, end = start + size - 1;
-
 	/*
 	 * If the new page is disjoint from the current range or is mapped at
 	 * a different granularity, then sync the TLB so that the gather
 	 * structure can be rewritten.
 	 */
-	if (gather->pgsize != size ||
-	    end + 1 < gather->start || start > gather->end + 1) {
-		if (gather->pgsize)
-			iommu_iotlb_sync(domain, gather);
-		gather->pgsize = size;
-	}
+	if ((gather->pgsize && gather->pgsize != size) ||
+	    iommu_iotlb_gather_is_disjoint(gather, iova, size))
+		iommu_iotlb_sync(domain, gather);
 
+	gather->pgsize = size;
 	iommu_iotlb_gather_add_range(gather, iova, size);
 }
 
@@ -730,6 +748,13 @@ static inline void iommu_iotlb_sync(struct iommu_domain *domain,
 {
 }
 
+static inline
+bool iommu_iotlb_gather_is_disjoint(struct iommu_iotlb_gather *gather,
+				    unsigned long iova, size_t size)
+{
+	return false;
+}
+
 static inline void iommu_iotlb_gather_add_range(struct iommu_iotlb_gather *gather,
 						unsigned long iova, size_t size)
 {
-- 
2.25.1