diff --git a/proxyclient/experiments/dart_dump.py b/proxyclient/experiments/dart_dump.py
index 2278b8ea..0c797ed3 100755
--- a/proxyclient/experiments/dart_dump.py
+++ b/proxyclient/experiments/dart_dump.py
@@ -52,7 +52,7 @@ class DART(RegMap):
     TTBR3           = irange(0x20c, 16, 16), R_TTBR
 
     def __init__(self, base):
-        super().__init__(p, base)
+        super().__init__(u, base)
         self.base = base
 
     def dump_table2(self, base, l1_addr):
diff --git a/proxyclient/m1n1/hv.py b/proxyclient/m1n1/hv.py
index 95d8de7e..267851e5 100644
--- a/proxyclient/m1n1/hv.py
+++ b/proxyclient/m1n1/hv.py
@@ -130,21 +130,7 @@ class HV(Reloadable):
             "p": self.p,
             "u": self.u,
             "TraceMode": TraceMode,
-        }
-        self.mmio_rd = [
-            lambda addr: [proxy.read8(addr)],
-            lambda addr: [proxy.read16(addr)],
-            lambda addr: [proxy.read32(addr)],
-            lambda addr: [proxy.read64(addr)],
-            lambda addr: [proxy.read64(addr), proxy.read64(addr + 8)],
-        ]
-        self.mmio_wr = [
-            lambda addr, data: proxy.write8(addr, data),
-            lambda addr, data: proxy.write16(addr, data),
-            lambda addr, data: proxy.write32(addr, data),
-            lambda addr, data: proxy.write64(addr, data),
-            lambda addr, data: (proxy.write64(addr, data[0]), proxy.write64(addr + 8, data[1])),
-        ]
+        })
 
         for attr in dir(self):
             a = getattr(self, attr)
@@ -336,9 +322,11 @@ class HV(Reloadable):
             first += 1
         elif mode == TraceMode.SYNC:
             if data.flags.WRITE:
-                self.mmio_wr[data.flags.WIDTH](data.addr, wval)
+                self.u.write(data.addr, wval, 8 << data.flags.WIDTH)
             else:
-                val = self.mmio_rd[data.flags.WIDTH](data.addr)
+                val = self.u.read(data.addr, 8 << data.flags.WIDTH)
+                if not isinstance(val, list) and not isinstance(val, tuple):
+                    val = [val]
         else:
             raise Exception(f"VM hook with unexpected mapping at {data.addr:#x}: {maps[0][0].name}")
 
diff --git a/proxyclient/m1n1/proxyutils.py b/proxyclient/m1n1/proxyutils.py
index 86bcd670..d7254bdb 100644
--- a/proxyclient/m1n1/proxyutils.py
+++ b/proxyclient/m1n1/proxyutils.py
@@ -68,6 +68,33 @@ class ProxyUtils(Reloadable):
             "gl2": (self.proxy.gl2_call, REGION_RX_EL1),
             "gl1": (self.proxy.gl1_call, 0),
         }
+        self._read = {
+            8: lambda addr: self.proxy.read8(addr),
+            16: lambda addr: self.proxy.read16(addr),
+            32: lambda addr: self.proxy.read32(addr),
+            64: lambda addr: self.proxy.read64(addr),
+            128: lambda addr: [self.proxy.read64(addr),
+                               self.proxy.read64(addr + 8)],
+        }
+        self._write = {
+            8: lambda addr, data: self.proxy.write8(addr, data),
+            16: lambda addr, data: self.proxy.write16(addr, data),
+            32: lambda addr, data: self.proxy.write32(addr, data),
+            64: lambda addr, data: self.proxy.write64(addr, data),
+            128: lambda addr, data: (self.proxy.write64(addr, data[0]),
+                                     self.proxy.write64(addr + 8, data[1])),
+        }
+
+    def read(self, addr, width):
+        val = self._read[width](addr)
+        if self.proxy.get_exc_count():
+            raise ProxyError("Exception occurred")
+        return val
+
+    def write(self, addr, data, width):
+        self._write[width](addr, data)
+        if self.proxy.get_exc_count():
+            raise ProxyError("Exception occurred")
 
     def mrs(self, reg, *, silent=False, call=None):
         op0, op1, CRn, CRm, op2 = sysreg_parse(reg)
diff --git a/proxyclient/m1n1/utils.py b/proxyclient/m1n1/utils.py
index c206dfe8..d7e0e9fb 100644
--- a/proxyclient/m1n1/utils.py
+++ b/proxyclient/m1n1/utils.py
@@ -558,8 +558,8 @@ class RegMap(Reloadable, metaclass=RegMeta):
 
         for name, (addr, rcls) in self._namemap.items():
             width = rcls.__WIDTH__
-            rd = getattr(backend, f"read{width}")
-            wr = getattr(backend, f"write{width}")
+            rd = lambda addr: backend.read(addr, width)
+            wr = lambda addr, data: backend.write(addr, data, width)
             if isinstance(addr, range):
                 self._accessor[name] = RegArrayAccessor(addr, rcls, rd, wr, base)
             else: