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-rw-r--r--hw/i386/intel_iommu.c4
-rw-r--r--hw/i386/intel_iommu_internal.h3
-rw-r--r--include/hw/i386/intel_iommu.h1
-rw-r--r--include/hw/i386/pc.h5
4 files changed, 13 insertions, 0 deletions
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 4806d7edb4..26cc731c7b 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -2659,6 +2659,7 @@ static Property vtd_properties[] = {
     DEFINE_PROP_UINT8("x-aw-bits", IntelIOMMUState, aw_bits,
                       VTD_HOST_ADDRESS_WIDTH),
     DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
+    DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
@@ -3147,6 +3148,9 @@ static void vtd_init(IntelIOMMUState *s)
     s->cap = VTD_CAP_FRO | VTD_CAP_NFR | VTD_CAP_ND |
              VTD_CAP_MAMV | VTD_CAP_PSI | VTD_CAP_SLLPS |
              VTD_CAP_SAGAW_39bit | VTD_CAP_MGAW(s->aw_bits);
+    if (s->dma_drain) {
+        s->cap |= VTD_CAP_DRAIN;
+    }
     if (s->aw_bits == VTD_HOST_AW_48BIT) {
         s->cap |= VTD_CAP_SAGAW_48bit;
     }
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index d084099ed9..00e9edbc66 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -203,6 +203,9 @@
 #define VTD_CAP_MAMV                (VTD_MAMV << 48)
 #define VTD_CAP_PSI                 (1ULL << 39)
 #define VTD_CAP_SLLPS               ((1ULL << 34) | (1ULL << 35))
+#define VTD_CAP_DRAIN_WRITE         (1ULL << 54)
+#define VTD_CAP_DRAIN_READ          (1ULL << 55)
+#define VTD_CAP_DRAIN               (VTD_CAP_DRAIN_READ | VTD_CAP_DRAIN_WRITE)
 #define VTD_CAP_CM                  (1ULL << 7)
 
 /* Supported Adjusted Guest Address Widths */
diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index ed4e758273..a321cc9691 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -245,6 +245,7 @@ struct IntelIOMMUState {
     OnOffAuto intr_eim;             /* Toggle for EIM cabability */
     bool buggy_eim;                 /* Force buggy EIM unless eim=off */
     uint8_t aw_bits;                /* Host/IOVA address width (in bits) */
+    bool dma_drain;                 /* Whether DMA r/w draining enabled */
 
     /*
      * Protects IOMMU states in general.  Currently it protects the
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 9d29c4b1df..c7c0c944e8 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -296,6 +296,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
 
 #define PC_COMPAT_3_1 \
     HW_COMPAT_3_1 \
+    {\
+        .driver   = "intel-iommu",\
+        .property = "dma-drain",\
+        .value    = "off",\
+    },
 
 #define PC_COMPAT_3_0 \
     HW_COMPAT_3_0 \