linux-kernel - [PATCH v2 5/7] iommu/vt-d: Enable DMA remapping after rmrr mapped

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Message-Id: <8880D5C8-8CEF-41C0-BD0D-1643945AD910@arista.com>
Date:   Thu, 14 Mar 2019 11:58:59 +0000
From:   James Sewart <jamessewart@...sta.com>
To:     iommu@...ts.linux-foundation.org
Cc:     Tom Murphy <tmurphy@...sta.com>, Dmitry Safonov <dima@...sta.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v2 5/7] iommu/vt-d: Enable DMA remapping after rmrr mapped

The rmrr devices require identity map of the rmrr regions before
enabling DMA remapping. Otherwise, there will be a window during
which DMA from/to the rmrr regions will be blocked. In order to
alleviate this, we move enabling DMA remapping after all rmrr
regions get mapped.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel-iommu.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 104d36f225a7..35821df70f78 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3518,11 +3518,6 @@ static int __init init_dmars(void)
 		ret = dmar_set_interrupt(iommu);
 		if (ret)
 			goto free_iommu;
-
-		if (!translation_pre_enabled(iommu))
-			iommu_enable_translation(iommu);
-
-		iommu_disable_protect_mem_regions(iommu);
 	}
 
 	return 0;
@@ -4912,7 +4907,6 @@ int __init intel_iommu_init(void)
 		goto out_free_reserved_range;
 	}
 	up_write(&dmar_global_lock);
-	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
 #if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
 	swiotlb = 0;
@@ -4935,6 +4929,16 @@ int __init intel_iommu_init(void)
 		register_memory_notifier(&intel_iommu_memory_nb);
 	cpuhp_setup_state(CPUHP_IOMMU_INTEL_DEAD, "iommu/intel:dead", NULL,
 			  intel_iommu_cpu_dead);
+
+	/* Finally, we enable the DMA remapping hardware. */
+	for_each_iommu(iommu, drhd) {
+		if (!translation_pre_enabled(iommu))
+			iommu_enable_translation(iommu);
+
+		iommu_disable_protect_mem_regions(iommu);
+	}
+	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
+
 	intel_iommu_enabled = 1;
 	intel_iommu_debugfs_init();
 
-- 
2.17.1