diff --git a/tests/libqos/virtio-mmio.c b/tests/libqos/virtio-mmio.c
index bced6803e6..7aa8383338 100644
--- a/tests/libqos/virtio-mmio.c
+++ b/tests/libqos/virtio-mmio.c
@@ -15,28 +15,28 @@
 #include "libqos/malloc-generic.h"
 #include "standard-headers/linux/virtio_ring.h"
 
-static uint8_t qvirtio_mmio_config_readb(QVirtioDevice *d, uint64_t addr)
+static uint8_t qvirtio_mmio_config_readb(QVirtioDevice *d, uint64_t off)
 {
     QVirtioMMIODevice *dev = (QVirtioMMIODevice *)d;
-    return readb(dev->addr + addr);
+    return readb(dev->addr + QVIRTIO_MMIO_DEVICE_SPECIFIC + off);
 }
 
-static uint16_t qvirtio_mmio_config_readw(QVirtioDevice *d, uint64_t addr)
+static uint16_t qvirtio_mmio_config_readw(QVirtioDevice *d, uint64_t off)
 {
     QVirtioMMIODevice *dev = (QVirtioMMIODevice *)d;
-    return readw(dev->addr + addr);
+    return readw(dev->addr + QVIRTIO_MMIO_DEVICE_SPECIFIC + off);
 }
 
-static uint32_t qvirtio_mmio_config_readl(QVirtioDevice *d, uint64_t addr)
+static uint32_t qvirtio_mmio_config_readl(QVirtioDevice *d, uint64_t off)
 {
     QVirtioMMIODevice *dev = (QVirtioMMIODevice *)d;
-    return readl(dev->addr + addr);
+    return readl(dev->addr + QVIRTIO_MMIO_DEVICE_SPECIFIC + off);
 }
 
-static uint64_t qvirtio_mmio_config_readq(QVirtioDevice *d, uint64_t addr)
+static uint64_t qvirtio_mmio_config_readq(QVirtioDevice *d, uint64_t off)
 {
     QVirtioMMIODevice *dev = (QVirtioMMIODevice *)d;
-    return readq(dev->addr + addr);
+    return readq(dev->addr + QVIRTIO_MMIO_DEVICE_SPECIFIC + off);
 }
 
 static uint32_t qvirtio_mmio_get_features(QVirtioDevice *d)
diff --git a/tests/libqos/virtio-pci.c b/tests/libqos/virtio-pci.c
index 7e60b3a427..fa82132ab7 100644
--- a/tests/libqos/virtio-pci.c
+++ b/tests/libqos/virtio-pci.c
@@ -62,10 +62,13 @@ static void qvirtio_pci_assign_device(QVirtioDevice *d, void *data)
     *vpcidev = (QVirtioPCIDevice *)d;
 }
 
-static uint8_t qvirtio_pci_config_readb(QVirtioDevice *d, uint64_t addr)
+#define CONFIG_BASE(dev) \
+    ((dev)->addr + VIRTIO_PCI_CONFIG_OFF((dev)->pdev->msix_enabled))
+
+static uint8_t qvirtio_pci_config_readb(QVirtioDevice *d, uint64_t off)
 {
     QVirtioPCIDevice *dev = (QVirtioPCIDevice *)d;
-    return qpci_io_readb(dev->pdev, (void *)(uintptr_t)addr);
+    return qpci_io_readb(dev->pdev, CONFIG_BASE(dev) + off);
 }
 
 /* PCI is always read in little-endian order
@@ -76,31 +79,31 @@ static uint8_t qvirtio_pci_config_readb(QVirtioDevice *d, uint64_t addr)
  * case will be managed inside qvirtio_is_big_endian()
  */
 
-static uint16_t qvirtio_pci_config_readw(QVirtioDevice *d, uint64_t addr)
+static uint16_t qvirtio_pci_config_readw(QVirtioDevice *d, uint64_t off)
 {
     QVirtioPCIDevice *dev = (QVirtioPCIDevice *)d;
     uint16_t value;
 
-    value = qpci_io_readw(dev->pdev, (void *)(uintptr_t)addr);
+    value = qpci_io_readw(dev->pdev, CONFIG_BASE(dev) + off);
     if (qvirtio_is_big_endian(d)) {
         value = bswap16(value);
     }
     return value;
 }
 
-static uint32_t qvirtio_pci_config_readl(QVirtioDevice *d, uint64_t addr)
+static uint32_t qvirtio_pci_config_readl(QVirtioDevice *d, uint64_t off)
 {
     QVirtioPCIDevice *dev = (QVirtioPCIDevice *)d;
     uint32_t value;
 
-    value = qpci_io_readl(dev->pdev, (void *)(uintptr_t)addr);
+    value = qpci_io_readl(dev->pdev, CONFIG_BASE(dev) + off);
     if (qvirtio_is_big_endian(d)) {
         value = bswap32(value);
     }
     return value;
 }
 
-static uint64_t qvirtio_pci_config_readq(QVirtioDevice *d, uint64_t addr)
+static uint64_t qvirtio_pci_config_readq(QVirtioDevice *d, uint64_t off)
 {
     QVirtioPCIDevice *dev = (QVirtioPCIDevice *)d;
     int i;
@@ -108,13 +111,13 @@ static uint64_t qvirtio_pci_config_readq(QVirtioDevice *d, uint64_t addr)
 
     if (qvirtio_is_big_endian(d)) {
         for (i = 0; i < 8; ++i) {
-            u64 |= (uint64_t)qpci_io_readb(dev->pdev,
-                                (void *)(uintptr_t)addr + i) << (7 - i) * 8;
+            u64 |= (uint64_t)qpci_io_readb(dev->pdev, CONFIG_BASE(dev)
+                                           + off + i) << (7 - i) * 8;
         }
     } else {
         for (i = 0; i < 8; ++i) {
-            u64 |= (uint64_t)qpci_io_readb(dev->pdev,
-                                (void *)(uintptr_t)addr + i) << i * 8;
+            u64 |= (uint64_t)qpci_io_readb(dev->pdev, CONFIG_BASE(dev)
+                                           + off + i) << i * 8;
         }
     }
 
diff --git a/tests/virtio-9p-test.c b/tests/virtio-9p-test.c
index 693920af5f..9c4f6cb406 100644
--- a/tests/virtio-9p-test.c
+++ b/tests/virtio-9p-test.c
@@ -95,7 +95,6 @@ static void qvirtio_9p_pci_free(QVirtIO9P *v9p)
 static void pci_basic_config(void)
 {
     QVirtIO9P *v9p;
-    void *addr;
     size_t tag_len;
     char *tag;
     int i;
@@ -104,15 +103,12 @@ static void pci_basic_config(void)
     qs = qvirtio_9p_start();
     v9p = qvirtio_9p_pci_init(qs);
 
-    addr = ((QVirtioPCIDevice *) v9p->dev)->addr + VIRTIO_PCI_CONFIG_OFF(false);
-    tag_len = qvirtio_config_readw(v9p->dev,
-                                   (uint64_t)(uintptr_t)addr);
+    tag_len = qvirtio_config_readw(v9p->dev, 0);
     g_assert_cmpint(tag_len, ==, strlen(mount_tag));
-    addr += sizeof(uint16_t);
 
     tag = g_malloc(tag_len);
     for (i = 0; i < tag_len; i++) {
-        tag[i] = qvirtio_config_readb(v9p->dev, (uint64_t)(uintptr_t)addr + i);
+        tag[i] = qvirtio_config_readb(v9p->dev, i + 2);
     }
     g_assert_cmpmem(tag, tag_len, mount_tag, tag_len);
     g_free(tag);
diff --git a/tests/virtio-blk-test.c b/tests/virtio-blk-test.c
index f737c406e3..0e32e416dd 100644
--- a/tests/virtio-blk-test.c
+++ b/tests/virtio-blk-test.c
@@ -155,7 +155,7 @@ static uint64_t virtio_blk_request(QGuestAllocator *alloc, QVirtioDevice *d,
 }
 
 static void test_basic(QVirtioDevice *dev, QGuestAllocator *alloc,
-                       QVirtQueue *vq, uint64_t device_specific)
+                       QVirtQueue *vq)
 {
     QVirtioBlkReq req;
     uint64_t req_addr;
@@ -165,7 +165,7 @@ static void test_basic(QVirtioDevice *dev, QGuestAllocator *alloc,
     uint8_t status;
     char *data;
 
-    capacity = qvirtio_config_readq(dev, device_specific);
+    capacity = qvirtio_config_readq(dev, 0);
 
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
@@ -285,17 +285,13 @@ static void pci_basic(void)
     QVirtioPCIDevice *dev;
     QOSState *qs;
     QVirtQueuePCI *vqpci;
-    void *addr;
 
     qs = pci_test_start();
     dev = virtio_blk_pci_init(qs->pcibus, PCI_SLOT);
 
     vqpci = (QVirtQueuePCI *)qvirtqueue_setup(&dev->vdev, qs->alloc, 0);
 
-    /* MSI-X is not enabled */
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(false);
-
-    test_basic(&dev->vdev, qs->alloc, &vqpci->vq, (uint64_t)(uintptr_t)addr);
+    test_basic(&dev->vdev, qs->alloc, &vqpci->vq);
 
     /* End test */
     qvirtqueue_cleanup(dev->vdev.bus, &vqpci->vq, qs->alloc);
@@ -311,7 +307,6 @@ static void pci_indirect(void)
     QOSState *qs;
     QVirtioBlkReq req;
     QVRingIndirectDesc *indirect;
-    void *addr;
     uint64_t req_addr;
     uint64_t capacity;
     uint32_t features;
@@ -323,10 +318,7 @@ static void pci_indirect(void)
 
     dev = virtio_blk_pci_init(qs->pcibus, PCI_SLOT);
 
-    /* MSI-X is not enabled */
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(false);
-
-    capacity = qvirtio_config_readq(&dev->vdev, (uint64_t)(uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
     features = qvirtio_get_features(&dev->vdev);
@@ -406,17 +398,13 @@ static void pci_config(void)
     QVirtioPCIDevice *dev;
     QOSState *qs;
     int n_size = TEST_IMAGE_SIZE / 2;
-    void *addr;
     uint64_t capacity;
 
     qs = pci_test_start();
 
     dev = virtio_blk_pci_init(qs->pcibus, PCI_SLOT);
 
-    /* MSI-X is not enabled */
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(false);
-
-    capacity = qvirtio_config_readq(&dev->vdev, (uint64_t)(uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
     qvirtio_set_driver_ok(&dev->vdev);
@@ -425,7 +413,7 @@ static void pci_config(void)
                                                     " 'size': %d } }", n_size);
     qvirtio_wait_config_isr(&dev->vdev, QVIRTIO_BLK_TIMEOUT_US);
 
-    capacity = qvirtio_config_readq(&dev->vdev, (uint64_t)(uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, n_size / 512);
 
     qvirtio_pci_device_disable(dev);
@@ -441,7 +429,6 @@ static void pci_msix(void)
     QVirtQueuePCI *vqpci;
     QVirtioBlkReq req;
     int n_size = TEST_IMAGE_SIZE / 2;
-    void *addr;
     uint64_t req_addr;
     uint64_t capacity;
     uint32_t features;
@@ -456,10 +443,7 @@ static void pci_msix(void)
 
     qvirtio_pci_set_msix_configuration_vector(dev, qs->alloc, 0);
 
-    /* MSI-X is enabled */
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(true);
-
-    capacity = qvirtio_config_readq(&dev->vdev, (uint64_t)(uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
     features = qvirtio_get_features(&dev->vdev);
@@ -479,7 +463,7 @@ static void pci_msix(void)
 
     qvirtio_wait_config_isr(&dev->vdev, QVIRTIO_BLK_TIMEOUT_US);
 
-    capacity = qvirtio_config_readq(&dev->vdev, (uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, n_size / 512);
 
     /* Write request */
@@ -550,7 +534,6 @@ static void pci_idx(void)
     QOSState *qs;
     QVirtQueuePCI *vqpci;
     QVirtioBlkReq req;
-    void *addr;
     uint64_t req_addr;
     uint64_t capacity;
     uint32_t features;
@@ -565,10 +548,7 @@ static void pci_idx(void)
 
     qvirtio_pci_set_msix_configuration_vector(dev, qs->alloc, 0);
 
-    /* MSI-X is enabled */
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(true);
-
-    capacity = qvirtio_config_readq(&dev->vdev, (uint64_t)(uintptr_t)addr);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
     features = qvirtio_get_features(&dev->vdev);
@@ -709,14 +689,14 @@ static void mmio_basic(void)
     alloc = generic_alloc_init(MMIO_RAM_ADDR, MMIO_RAM_SIZE, MMIO_PAGE_SIZE);
     vq = qvirtqueue_setup(&dev->vdev, alloc, 0);
 
-    test_basic(&dev->vdev, alloc, vq, QVIRTIO_MMIO_DEVICE_SPECIFIC);
+    test_basic(&dev->vdev, alloc, vq);
 
     qmp("{ 'execute': 'block_resize', 'arguments': { 'device': 'drive0', "
                                                     " 'size': %d } }", n_size);
 
     qvirtio_wait_queue_isr(&dev->vdev, vq, QVIRTIO_BLK_TIMEOUT_US);
 
-    capacity = qvirtio_config_readq(&dev->vdev, QVIRTIO_MMIO_DEVICE_SPECIFIC);
+    capacity = qvirtio_config_readq(&dev->vdev, 0);
     g_assert_cmpint(capacity, ==, n_size / 512);
 
     /* End test */
diff --git a/tests/virtio-scsi-test.c b/tests/virtio-scsi-test.c
index 60dc9abd60..69220ef07b 100644
--- a/tests/virtio-scsi-test.c
+++ b/tests/virtio-scsi-test.c
@@ -143,7 +143,6 @@ static QVirtIOSCSI *qvirtio_scsi_pci_init(int slot)
     QVirtIOSCSI *vs;
     QVirtioPCIDevice *dev;
     struct virtio_scsi_cmd_resp resp;
-    void *addr;
     int i;
 
     vs = g_new0(QVirtIOSCSI, 1);
@@ -161,8 +160,7 @@ static QVirtIOSCSI *qvirtio_scsi_pci_init(int slot)
     qvirtio_set_acknowledge(vs->dev);
     qvirtio_set_driver(vs->dev);
 
-    addr = dev->addr + VIRTIO_PCI_CONFIG_OFF(false);
-    vs->num_queues = qvirtio_config_readl(vs->dev, (uint64_t)(uintptr_t)addr);
+    vs->num_queues = qvirtio_config_readl(vs->dev, 0);
 
     g_assert_cmpint(vs->num_queues, <, MAX_NUM_QUEUES);