diff --git a/include/exec/memattrs.h b/include/exec/memattrs.h
new file mode 100644
index 0000000..b8d7808
--- /dev/null
+++ b/include/exec/memattrs.h
@@ -0,0 +1,34 @@
+/*
+ * Memory transaction attributes
+ *
+ * Copyright (c) 2015 Linaro Limited.
+ *
+ * Authors:
+ *  Peter Maydell <peter.maydell@linaro.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef MEMATTRS_H
+#define MEMATTRS_H
+
+/* Every memory transaction has associated with it a set of
+ * attributes. Some of these are generic (such as the ID of
+ * the bus master); some are specific to a particular kind of
+ * bus (such as the ARM Secure/NonSecure bit). We define them
+ * all as non-overlapping bits in a single integer to avoid
+ * confusion if different parts of QEMU used the same bit for
+ * different semantics.
+ */
+typedef uint64_t MemTxAttrs;
+
+/* Bus masters which don't specify any attributes will get this,
+ * which has all attribute bits clear except the topmost one
+ * (so that we can distinguish "all attributes deliberately clear"
+ * from "didn't specify" if necessary).
+ */
+#define MEMTXATTRS_UNSPECIFIED (1ULL << 63)
+
+#endif
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 06ffa1d..703d9e5 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -28,6 +28,7 @@
 #ifndef CONFIG_USER_ONLY
 #include "exec/hwaddr.h"
 #endif
+#include "exec/memattrs.h"
 #include "qemu/queue.h"
 #include "qemu/int128.h"
 #include "qemu/notify.h"
@@ -68,6 +69,16 @@ struct IOMMUTLBEntry {
     IOMMUAccessFlags perm;
 };
 
+/* New-style MMIO accessors can indicate that the transaction failed.
+ * A zero (MEMTX_OK) response means success; anything else is a failure
+ * of some kind. The memory subsystem will bitwise-OR together results
+ * if it is synthesizing an operation from multiple smaller accesses.
+ */
+#define MEMTX_OK 0
+#define MEMTX_ERROR             (1U << 0) /* device returned an error */
+#define MEMTX_DECODE_ERROR      (1U << 1) /* nothing at that address */
+typedef uint32_t MemTxResult;
+
 /*
  * Memory region callbacks
  */
@@ -84,6 +95,17 @@ struct MemoryRegionOps {
                   uint64_t data,
                   unsigned size);
 
+    MemTxResult (*read_with_attrs)(void *opaque,
+                                   hwaddr addr,
+                                   uint64_t *data,
+                                   unsigned size,
+                                   MemTxAttrs attrs);
+    MemTxResult (*write_with_attrs)(void *opaque,
+                                    hwaddr addr,
+                                    uint64_t data,
+                                    unsigned size,
+                                    MemTxAttrs attrs);
+
     enum device_endian endianness;
     /* Guest-visible constraints: */
     struct {
diff --git a/memory.c b/memory.c
index ee3f2a8..9bb5674 100644
--- a/memory.c
+++ b/memory.c
@@ -368,57 +368,84 @@ static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
     }
 }
 
-static void memory_region_oldmmio_read_accessor(MemoryRegion *mr,
+static MemTxResult memory_region_oldmmio_read_accessor(MemoryRegion *mr,
+                                                       hwaddr addr,
+                                                       uint64_t *value,
+                                                       unsigned size,
+                                                       unsigned shift,
+                                                       uint64_t mask,
+                                                       MemTxAttrs attrs)
+{
+    uint64_t tmp;
+
+    tmp = mr->ops->old_mmio.read[ctz32(size)](mr->opaque, addr);
+    trace_memory_region_ops_read(mr, addr, tmp, size);
+    *value |= (tmp & mask) << shift;
+    return MEMTX_OK;
+}
+
+static MemTxResult  memory_region_read_accessor(MemoryRegion *mr,
                                                 hwaddr addr,
                                                 uint64_t *value,
                                                 unsigned size,
                                                 unsigned shift,
-                                                uint64_t mask)
+                                                uint64_t mask,
+                                                MemTxAttrs attrs)
 {
     uint64_t tmp;
 
-    tmp = mr->ops->old_mmio.read[ctz32(size)](mr->opaque, addr);
+    if (mr->flush_coalesced_mmio) {
+        qemu_flush_coalesced_mmio_buffer();
+    }
+    tmp = mr->ops->read(mr->opaque, addr, size);
     trace_memory_region_ops_read(mr, addr, tmp, size);
     *value |= (tmp & mask) << shift;
+    return MEMTX_OK;
 }
 
-static void memory_region_read_accessor(MemoryRegion *mr,
-                                        hwaddr addr,
-                                        uint64_t *value,
-                                        unsigned size,
-                                        unsigned shift,
-                                        uint64_t mask)
+static MemTxResult memory_region_read_with_attrs_accessor(MemoryRegion *mr,
+                                                          hwaddr addr,
+                                                          uint64_t *value,
+                                                          unsigned size,
+                                                          unsigned shift,
+                                                          uint64_t mask,
+                                                          MemTxAttrs attrs)
 {
-    uint64_t tmp;
+    uint64_t tmp = 0;
+    MemTxResult r;
 
     if (mr->flush_coalesced_mmio) {
         qemu_flush_coalesced_mmio_buffer();
     }
-    tmp = mr->ops->read(mr->opaque, addr, size);
+    r = mr->ops->read_with_attrs(mr->opaque, addr, &tmp, size, attrs);
     trace_memory_region_ops_read(mr, addr, tmp, size);
     *value |= (tmp & mask) << shift;
+    return r;
 }
 
-static void memory_region_oldmmio_write_accessor(MemoryRegion *mr,
-                                                 hwaddr addr,
-                                                 uint64_t *value,
-                                                 unsigned size,
-                                                 unsigned shift,
-                                                 uint64_t mask)
+static MemTxResult memory_region_oldmmio_write_accessor(MemoryRegion *mr,
+                                                        hwaddr addr,
+                                                        uint64_t *value,
+                                                        unsigned size,
+                                                        unsigned shift,
+                                                        uint64_t mask,
+                                                        MemTxAttrs attrs)
 {
     uint64_t tmp;
 
     tmp = (*value >> shift) & mask;
     trace_memory_region_ops_write(mr, addr, tmp, size);
     mr->ops->old_mmio.write[ctz32(size)](mr->opaque, addr, tmp);
+    return MEMTX_OK;
 }
 
-static void memory_region_write_accessor(MemoryRegion *mr,
-                                         hwaddr addr,
-                                         uint64_t *value,
-                                         unsigned size,
-                                         unsigned shift,
-                                         uint64_t mask)
+static MemTxResult memory_region_write_accessor(MemoryRegion *mr,
+                                                hwaddr addr,
+                                                uint64_t *value,
+                                                unsigned size,
+                                                unsigned shift,
+                                                uint64_t mask,
+                                                MemTxAttrs attrs)
 {
     uint64_t tmp;
 
@@ -428,24 +455,46 @@ static void memory_region_write_accessor(MemoryRegion *mr,
     tmp = (*value >> shift) & mask;
     trace_memory_region_ops_write(mr, addr, tmp, size);
     mr->ops->write(mr->opaque, addr, tmp, size);
+    return MEMTX_OK;
 }
 
-static void access_with_adjusted_size(hwaddr addr,
+static MemTxResult memory_region_write_with_attrs_accessor(MemoryRegion *mr,
+                                                           hwaddr addr,
+                                                           uint64_t *value,
+                                                           unsigned size,
+                                                           unsigned shift,
+                                                           uint64_t mask,
+                                                           MemTxAttrs attrs)
+{
+    uint64_t tmp;
+
+    if (mr->flush_coalesced_mmio) {
+        qemu_flush_coalesced_mmio_buffer();
+    }
+    tmp = (*value >> shift) & mask;
+    trace_memory_region_ops_write(mr, addr, tmp, size);
+    return mr->ops->write_with_attrs(mr->opaque, addr, tmp, size, attrs);
+}
+
+static MemTxResult access_with_adjusted_size(hwaddr addr,
                                       uint64_t *value,
                                       unsigned size,
                                       unsigned access_size_min,
                                       unsigned access_size_max,
-                                      void (*access)(MemoryRegion *mr,
-                                                     hwaddr addr,
-                                                     uint64_t *value,
-                                                     unsigned size,
-                                                     unsigned shift,
-                                                     uint64_t mask),
-                                      MemoryRegion *mr)
+                                      MemTxResult (*access)(MemoryRegion *mr,
+                                                            hwaddr addr,
+                                                            uint64_t *value,
+                                                            unsigned size,
+                                                            unsigned shift,
+                                                            uint64_t mask,
+                                                            MemTxAttrs attrs),
+                                      MemoryRegion *mr,
+                                      MemTxAttrs attrs)
 {
     uint64_t access_mask;
     unsigned access_size;
     unsigned i;
+    MemTxResult r = MEMTX_OK;
 
     if (!access_size_min) {
         access_size_min = 1;
@@ -459,14 +508,16 @@ static void access_with_adjusted_size(hwaddr addr,
     access_mask = -1ULL >> (64 - access_size * 8);
     if (memory_region_big_endian(mr)) {
         for (i = 0; i < size; i += access_size) {
-            access(mr, addr + i, value, access_size,
-                   (size - access_size - i) * 8, access_mask);
+            r |= access(mr, addr + i, value, access_size,
+                        (size - access_size - i) * 8, access_mask, attrs);
         }
     } else {
         for (i = 0; i < size; i += access_size) {
-            access(mr, addr + i, value, access_size, i * 8, access_mask);
+            r |= access(mr, addr + i, value, access_size, i * 8,
+                        access_mask, attrs);
         }
     }
+    return r;
 }
 
 static AddressSpace *memory_region_to_address_space(MemoryRegion *mr)
@@ -1053,62 +1104,82 @@ bool memory_region_access_valid(MemoryRegion *mr,
     return true;
 }
 
-static uint64_t memory_region_dispatch_read1(MemoryRegion *mr,
-                                             hwaddr addr,
-                                             unsigned size)
+static MemTxResult memory_region_dispatch_read1(MemoryRegion *mr,
+                                                hwaddr addr,
+                                                uint64_t *pval,
+                                                unsigned size,
+                                                MemTxAttrs attrs)
 {
-    uint64_t data = 0;
+    *pval = 0;
 
     if (mr->ops->read) {
-        access_with_adjusted_size(addr, &data, size,
-                                  mr->ops->impl.min_access_size,
-                                  mr->ops->impl.max_access_size,
-                                  memory_region_read_accessor, mr);
+        return access_with_adjusted_size(addr, pval, size,
+                                         mr->ops->impl.min_access_size,
+                                         mr->ops->impl.max_access_size,
+                                         memory_region_read_accessor,
+                                         mr, attrs);
+    } else if (mr->ops->read_with_attrs) {
+        return access_with_adjusted_size(addr, pval, size,
+                                         mr->ops->impl.min_access_size,
+                                         mr->ops->impl.max_access_size,
+                                         memory_region_read_with_attrs_accessor,
+                                         mr, attrs);
     } else {
-        access_with_adjusted_size(addr, &data, size, 1, 4,
-                                  memory_region_oldmmio_read_accessor, mr);
+        return access_with_adjusted_size(addr, pval, size, 1, 4,
+                                         memory_region_oldmmio_read_accessor,
+                                         mr, attrs);
     }
-
-    return data;
 }
 
-static bool memory_region_dispatch_read(MemoryRegion *mr,
-                                        hwaddr addr,
-                                        uint64_t *pval,
-                                        unsigned size)
+static MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
+                                               hwaddr addr,
+                                               uint64_t *pval,
+                                               unsigned size,
+                                               MemTxAttrs attrs)
 {
+    MemTxResult r;
+
     if (!memory_region_access_valid(mr, addr, size, false)) {
         *pval = unassigned_mem_read(mr, addr, size);
-        return true;
+        return MEMTX_DECODE_ERROR;
     }
 
-    *pval = memory_region_dispatch_read1(mr, addr, size);
+    r = memory_region_dispatch_read1(mr, addr, pval, size, attrs);
     adjust_endianness(mr, pval, size);
-    return false;
+    return r;
 }
 
-static bool memory_region_dispatch_write(MemoryRegion *mr,
-                                         hwaddr addr,
-                                         uint64_t data,
-                                         unsigned size)
+static MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
+                                                hwaddr addr,
+                                                uint64_t data,
+                                                unsigned size,
+                                                MemTxAttrs attrs)
 {
     if (!memory_region_access_valid(mr, addr, size, true)) {
         unassigned_mem_write(mr, addr, data, size);
-        return true;
+        return MEMTX_DECODE_ERROR;
     }
 
     adjust_endianness(mr, &data, size);
 
     if (mr->ops->write) {
-        access_with_adjusted_size(addr, &data, size,
-                                  mr->ops->impl.min_access_size,
-                                  mr->ops->impl.max_access_size,
-                                  memory_region_write_accessor, mr);
+        return access_with_adjusted_size(addr, &data, size,
+                                         mr->ops->impl.min_access_size,
+                                         mr->ops->impl.max_access_size,
+                                         memory_region_write_accessor, mr,
+                                         attrs);
+    } else if (mr->ops->write_with_attrs) {
+        return
+            access_with_adjusted_size(addr, &data, size,
+                                      mr->ops->impl.min_access_size,
+                                      mr->ops->impl.max_access_size,
+                                      memory_region_write_with_attrs_accessor,
+                                      mr, attrs);
     } else {
-        access_with_adjusted_size(addr, &data, size, 1, 4,
-                                  memory_region_oldmmio_write_accessor, mr);
+        return access_with_adjusted_size(addr, &data, size, 1, 4,
+                                         memory_region_oldmmio_write_accessor,
+                                         mr, attrs);
     }
-    return false;
 }
 
 void memory_region_init_io(MemoryRegion *mr,
@@ -1994,13 +2065,15 @@ void address_space_destroy(AddressSpace *as)
 
 bool io_mem_read(MemoryRegion *mr, hwaddr addr, uint64_t *pval, unsigned size)
 {
-    return memory_region_dispatch_read(mr, addr, pval, size);
+    return memory_region_dispatch_read(mr, addr, pval, size,
+                                       MEMTXATTRS_UNSPECIFIED);
 }
 
 bool io_mem_write(MemoryRegion *mr, hwaddr addr,
                   uint64_t val, unsigned size)
 {
-    return memory_region_dispatch_write(mr, addr, val, size);
+    return memory_region_dispatch_write(mr, addr, val, size,
+                                        MEMTXATTRS_UNSPECIFIED);
 }
 
 typedef struct MemoryRegionList MemoryRegionList;
