Patch "iommu/vt-d: Enable QI on all IOMMUs before setting root entry" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

iommu/vt-d: Enable QI on all IOMMUs before setting root entry

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iommu-vt-d-enable-qi-on-all-iommus-before-setting-root-entry.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Joerg Roedel <[email protected]>
Date: Fri, 17 Jun 2016 11:29:48 +0200
Subject: iommu/vt-d: Enable QI on all IOMMUs before setting root entry

From: Joerg Roedel <[email protected]>

commit a4c34ff1c029e90e7d5f8dd8d29b0a93b31c3cb2 upstream.

This seems to be required on some X58 chipsets on systems with more than one IOMMU. QI does not work until it is enabled on all IOMMUs in the system.

---
 drivers/iommu/intel-iommu.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

@@ -3169,11 +3169,6 @@ static int __init init_dmars(void)
 			}
 		}
 
-		iommu_flush_write_buffer(iommu);
-		iommu_set_root_entry(iommu);
-		iommu->flush.flush_context(iommu, 0, 0, 0, DMA_CCMD_GLOBAL_INVL);
-		iommu->flush.flush_iotlb(iommu, 0, 0, 0, DMA_TLB_GLOBAL_FLUSH);
-
 		if (!ecap_pass_through(iommu->ecap))
 			hw_pass_through = 0;
 #ifdef CONFIG_INTEL_IOMMU_SVM

@@ -3182,6 +3177,18 @@ static int __init init_dmars(void)
 #endif
 	}
 
+	/*
+	 * Now that qi is enabled on all iommus, set the root entry and flush
+	 * caches. This is required on some Intel X58 chipsets, otherwise the
+	 * flush_context function will loop forever and the boot hangs.
+	 */
+	for_each_active_iommu(iommu, drhd) {
+		iommu_flush_write_buffer(iommu);
+		iommu_set_root_entry(iommu);
+		iommu->flush.flush_context(iommu, 0, 0, 0, DMA_CCMD_GLOBAL_INVL);
+		iommu->flush.flush_iotlb(iommu, 0, 0, 0, DMA_TLB_GLOBAL_FLUSH);
+	}
+
 	if (iommu_pass_through)
 		iommu_identity_mapping |= IDENTMAP_ALL;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/iommu-vt-d-enable-qi-on-all-iommus-before-setting-root-entry.patch queue-4.4/iommu-amd-fix-unity-mapping-initialization-race.patch queue-4.4/iommu-arm-smmu-wire-up-map_sg-for-arm-smmu-v3.patch