diff --git a/[refs] b/[refs]
index 56bb4618fe45..f7f7dcf6c614 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 988f0e24bbcbbf550dff016faf8273a94f4eb1af
+refs/heads/master: fc2341df9e31be8a3940f4e302372d7ef46bab8c
diff --git a/trunk/arch/x86/xen/pci-swiotlb-xen.c b/trunk/arch/x86/xen/pci-swiotlb-xen.c
index b6a534002ab2..1c1722761eec 100644
--- a/trunk/arch/x86/xen/pci-swiotlb-xen.c
+++ b/trunk/arch/x86/xen/pci-swiotlb-xen.c
@@ -8,6 +8,11 @@
 #include <xen/xen.h>
 #include <asm/iommu_table.h>
 
+#ifdef CONFIG_X86_64
+#include <asm/iommu.h>
+#include <asm/dma.h>
+#endif
+
 int xen_swiotlb __read_mostly;
 
 static struct dma_map_ops xen_swiotlb_dma_ops = {
@@ -49,6 +54,15 @@ int __init pci_xen_swiotlb_detect(void)
 	 * the 'swiotlb' flag is the only one turning it on. */
 	swiotlb = 0;
 
+#ifdef CONFIG_X86_64
+	/* pci_swiotlb_detect_4gb turns on native SWIOTLB if no_iommu == 0
+	 * (so no iommu=X command line over-writes).
+	 * Considering that PV guests do not want the *native SWIOTLB* but
+	 * only Xen SWIOTLB it is not useful to us so set no_iommu=1 here.
+	 */
+	if (max_pfn > MAX_DMA32_PFN)
+		no_iommu = 1;
+#endif
 	return xen_swiotlb;
 }