Patch "iommu/amd: Fix unity mapping initialization race" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    iommu/amd: Fix unity mapping initialization race

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-amd-fix-unity-mapping-initialization-race.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 <stable@vger.kernel.org> know about it.


>From 522e5cb76d0663c88f96b6a8301451c8efa37207 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Fri, 1 Jul 2016 16:42:55 +0200
Subject: iommu/amd: Fix unity mapping initialization race

From: Joerg Roedel <jroedel@suse.de>

commit 522e5cb76d0663c88f96b6a8301451c8efa37207 upstream.

There is a race condition in the AMD IOMMU init code that
causes requested unity mappings to be blocked by the IOMMU
for a short period of time. This results on boot failures
and IO_PAGE_FAULTs on some machines.

Fix this by making sure the unity mappings are installed
before all other DMA is blocked.

Fixes: aafd8ba0ca74 ('iommu/amd: Implement add_device and remove_device')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iommu/amd_iommu_init.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1363,13 +1363,23 @@ static int __init amd_iommu_init_pci(voi
 			break;
 	}
 
+	/*
+	 * Order is important here to make sure any unity map requirements are
+	 * fulfilled. The unity mappings are created and written to the device
+	 * table during the amd_iommu_init_api() call.
+	 *
+	 * After that we call init_device_table_dma() to make sure any
+	 * uninitialized DTE will block DMA, and in the end we flush the caches
+	 * of all IOMMUs to make sure the changes to the device table are
+	 * active.
+	 */
+	ret = amd_iommu_init_api();
+
 	init_device_table_dma();
 
 	for_each_iommu(iommu)
 		iommu_flush_all_caches(iommu);
 
-	ret = amd_iommu_init_api();
-
 	if (!ret)
 		print_iommu_info();
 


Patches currently in stable-queue which might be from jroedel@suse.de 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