diff --git a/hw/misc/pc-testdev.c b/hw/misc/pc-testdev.c
index ad1aa660d4..5867c70069 100644
--- a/hw/misc/pc-testdev.c
+++ b/hw/misc/pc-testdev.c
@@ -49,6 +49,7 @@ typedef struct PCTestdev {
     ISADevice parent_obj;
 
     MemoryRegion ioport;
+    MemoryRegion ioport_byte;
     MemoryRegion flush;
     MemoryRegion irq;
     MemoryRegion iomem;
@@ -102,6 +103,16 @@ static const MemoryRegionOps test_ioport_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
+static const MemoryRegionOps test_ioport_byte_ops = {
+    .read = test_ioport_read,
+    .write = test_ioport_write,
+    .valid.min_access_size = 1,
+    .valid.max_access_size = 4,
+    .impl.min_access_size = 1,
+    .impl.max_access_size = 1,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
 static void test_flush_page(void *opaque, hwaddr addr, uint64_t data,
                             unsigned len)
 {
@@ -156,6 +167,9 @@ static void testdev_realizefn(DeviceState *d, Error **errp)
 
     memory_region_init_io(&dev->ioport, OBJECT(dev), &test_ioport_ops, dev,
                           "pc-testdev-ioport", 4);
+    memory_region_init_io(&dev->ioport_byte, OBJECT(dev),
+                          &test_ioport_byte_ops, dev,
+                          "pc-testdev-ioport-byte", 4);
     memory_region_init_io(&dev->flush, OBJECT(dev), &test_flush_ops, dev,
                           "pc-testdev-flush-page", 4);
     memory_region_init_io(&dev->irq, OBJECT(dev), &test_irq_ops, dev,
@@ -165,6 +179,7 @@ static void testdev_realizefn(DeviceState *d, Error **errp)
 
     memory_region_add_subregion(io,  0xe0,       &dev->ioport);
     memory_region_add_subregion(io,  0xe4,       &dev->flush);
+    memory_region_add_subregion(io,  0xe8,       &dev->ioport_byte);
     memory_region_add_subregion(io,  0x2000,     &dev->irq);
     memory_region_add_subregion(mem, 0xff000000, &dev->iomem);
 }
diff --git a/tests/endianness-test.c b/tests/endianness-test.c
index ca666456bc..feb32a8503 100644
--- a/tests/endianness-test.c
+++ b/tests/endianness-test.c
@@ -190,6 +190,100 @@ static void test_endianness(gconstpointer data)
     g_free(args);
 }
 
+static void test_endianness_split(gconstpointer data)
+{
+    const TestCase *test = data;
+    char *args;
+
+    args = g_strdup_printf("-display none -M %s%s%s -device pc-testdev",
+                           test->machine,
+                           test->superio ? " -device " : "",
+                           test->superio ?: "");
+    qtest_start(args);
+    isa_outl(test, 0xe8, 0x87654321);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x87654321);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4321);
+
+    isa_outw(test, 0xea, 0x8866);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x88664321);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8866);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4321);
+
+    isa_outw(test, 0xe8, 0x4422);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x88664422);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8866);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4422);
+
+    isa_outb(test, 0xeb, 0x87);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x87664422);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8766);
+
+    isa_outb(test, 0xea, 0x65);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x87654422);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4422);
+
+    isa_outb(test, 0xe9, 0x43);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x87654322);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4322);
+
+    isa_outb(test, 0xe8, 0x21);
+    g_assert_cmphex(isa_inl(test, 0xe0), ==, 0x87654321);
+    g_assert_cmphex(isa_inw(test, 0xe2), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe0), ==, 0x4321);
+    qtest_quit(global_qtest);
+    g_free(args);
+}
+
+static void test_endianness_combine(gconstpointer data)
+{
+    const TestCase *test = data;
+    char *args;
+
+    args = g_strdup_printf("-display none -M %s%s%s -device pc-testdev",
+                           test->machine,
+                           test->superio ? " -device " : "",
+                           test->superio ?: "");
+    qtest_start(args);
+    isa_outl(test, 0xe0, 0x87654321);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x87654321);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4321);
+
+    isa_outw(test, 0xe2, 0x8866);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x88664321);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8866);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4321);
+
+    isa_outw(test, 0xe0, 0x4422);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x88664422);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8866);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4422);
+
+    isa_outb(test, 0xe3, 0x87);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x87664422);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8766);
+
+    isa_outb(test, 0xe2, 0x65);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x87654422);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4422);
+
+    isa_outb(test, 0xe1, 0x43);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x87654322);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4322);
+
+    isa_outb(test, 0xe0, 0x21);
+    g_assert_cmphex(isa_inl(test, 0xe8), ==, 0x87654321);
+    g_assert_cmphex(isa_inw(test, 0xea), ==, 0x8765);
+    g_assert_cmphex(isa_inw(test, 0xe8), ==, 0x4321);
+    qtest_quit(global_qtest);
+    g_free(args);
+}
+
 int main(int argc, char **argv)
 {
     const char *arch = qtest_get_arch();
@@ -206,6 +300,14 @@ int main(int argc, char **argv)
         path = g_strdup_printf("/%s/endianness/%s",
                                arch, test_cases[i].machine);
         g_test_add_data_func(path, &test_cases[i], test_endianness);
+
+        path = g_strdup_printf("/%s/endianness/split/%s",
+                               arch, test_cases[i].machine);
+        g_test_add_data_func(path, &test_cases[i], test_endianness_split);
+
+        path = g_strdup_printf("/%s/endianness/combine/%s",
+                               arch, test_cases[i].machine);
+        g_test_add_data_func(path, &test_cases[i], test_endianness_combine);
     }
 
     ret = g_test_run();