linux-kernel - [PATCH 1/1] iommu/vt-d: Use real PASID for flush in caching mode

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Date:   Fri, 16 Mar 2018 12:31:36 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Sankaran Rajesh <rajesh.sankaran@...el.com>,
        Liu Yi L <yi.l.liu@...el.com>
Subject: [PATCH 1/1] iommu/vt-d: Use real PASID for flush in caching mode

If caching mode is supported, the hardware will cache
none-present or erroneous translation entries. Hence,
software should explicitly invalidate the PASID cache
after a PASID table entry becomes present. We should
issue such invalidation with the PASID value that we
have changed. PASID 0 is not reserved for this case.

Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: Kevin Tian <kevin.tian@...el.com>
Cc: Sankaran Rajesh <rajesh.sankaran@...el.com>
Suggested-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel-svm.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 99bc9bd..b7b88b5 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -422,17 +422,13 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_
 		iommu->pasid_table[svm->pasid].val = pasid_entry_val;
 
 		wmb();
-		/* In caching mode, we still have to flush with PASID 0 when
-		 * a PASID table entry becomes present. Not entirely clear
-		 * *why* that would be the case — surely we could just issue
-		 * a flush with the PASID value that we've changed? The PASID
-		 * is the index into the table, after all. It's not like domain
-		 * IDs in the case of the equivalent context-entry change in
-		 * caching mode. And for that matter it's not entirely clear why
-		 * a VMM would be in the business of caching the PASID table
-		 * anyway. Surely that can be left entirely to the guest? */
+
+		/*
+		 * Flush PASID cache when a PASID table entry becomes
+		 * present.
+		 */
 		if (cap_caching_mode(iommu->cap))
-			intel_flush_pasid_dev(svm, sdev, 0);
+			intel_flush_pasid_dev(svm, sdev, svm->pasid);
 	}
 	list_add_rcu(&sdev->list, &svm->devs);
 
-- 
2.7.4