1 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index b6a534002ab2..1c1722761eec 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/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;
 }