Patch "iommu/vt-d: Flush the IOTLB to get rid of the initial kdump mappings" has been added to the 4.9-stable tree

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

iommu/vt-d: Flush the IOTLB to get rid of the initial kdump mappings

to the 4.9-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-flush-the-iotlb-to-get-rid-of-the-initial-kdump-mappings.patch
and it can be found in the queue-4.9 subdirectory.

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

From: KarimAllah Ahmed <[email protected]>
Date: Fri, 5 May 2017 11:39:59 -0700
Subject: iommu/vt-d: Flush the IOTLB to get rid of the initial kdump mappings

From: KarimAllah Ahmed <[email protected]>

commit f73a7eee900e95404b61408a23a1df5c5811704c upstream.

Ever since commit 091d42e43d ("iommu/vt-d: Copy translation tables from old kernel") the kdump kernel copies the IOMMU context tables from the previous kernel. Each device mappings will be destroyed once the driver for the respective device takes over.

This unfortunately breaks the workflow of mapping and unmapping a new context to the IOMMU. The mapping function assumes that either:

1) Unmapping did the proper IOMMU flushing and it only ever flush if the IOMMU unit supports caching invalid entries.
2) The system just booted and the initialization code took care of flushing all IOMMU caches.

This assumption is not true for the kdump kernel since the context tables have been copied from the previous kernel and translations could have been cached ever since. So make sure to flush the IOTLB as well when we destroy these old copied mappings.

---
 drivers/iommu/intel-iommu.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

@@ -2049,11 +2049,14 @@ static int domain_context_mapping_one(st
 	if (context_copied(context)) {
 		u16 did_old = context_domain_id(context);
 
-		if (did_old >= 0 && did_old < cap_ndoms(iommu->cap))
+		if (did_old >= 0 && did_old < cap_ndoms(iommu->cap)) {
 			iommu->flush.flush_context(iommu, did_old,
 						   (((u16)bus) << 8) | devfn,
 						   DMA_CCMD_MASK_NOBIT,
 						   DMA_CCMD_DEVICE_INVL);
+			iommu->flush.flush_iotlb(iommu, did_old, 0, 0,
+						 DMA_TLB_DSI_FLUSH);
+		}
 	}
 
 	pgd = domain->pgd;

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

queue-4.9/iommu-vt-d-flush-the-iotlb-to-get-rid-of-the-initial-kdump-mappings.patch