The VIRTIO Configuration Space cannot be accessed before device feature
bits have been read because a driver doesn't know the endianness until
it has checked VIRTIO_F_VERSION_1.

Fix this problem in preparation for VIRTIO 1.0 support.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/virtio-blk-test.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/tests/virtio-blk-test.c b/tests/virtio-blk-test.c
index ed13167392..f6674fb233 100644
--- a/tests/virtio-blk-test.c
+++ b/tests/virtio-blk-test.c
@@ -125,10 +125,6 @@ static void test_basic(QVirtioDevice *dev, QGuestAllocator *alloc,
     char *data;
     QTestState *qts = global_qtest;
 
-    capacity = qvirtio_config_readq(dev, 0);
-
-    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
-
     features = qvirtio_get_features(dev);
     features = features & ~(QVIRTIO_F_BAD_FEATURE |
                     (1u << VIRTIO_RING_F_INDIRECT_DESC) |
@@ -136,6 +132,9 @@ static void test_basic(QVirtioDevice *dev, QGuestAllocator *alloc,
                     (1u << VIRTIO_BLK_F_SCSI));
     qvirtio_set_features(dev, features);
 
+    capacity = qvirtio_config_readq(dev, 0);
+    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
+
     qvirtio_set_driver_ok(dev);
 
     /* Write and read with 3 descriptor layout */
@@ -359,9 +358,6 @@ static void indirect(void *obj, void *u_data, QGuestAllocator *t_alloc)
     char *data;
     QTestState *qts = global_qtest;
 
-    capacity = qvirtio_config_readq(dev, 0);
-    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
-
     features = qvirtio_get_features(dev);
     g_assert_cmphex(features & (1u << VIRTIO_RING_F_INDIRECT_DESC), !=, 0);
     features = features & ~(QVIRTIO_F_BAD_FEATURE |
@@ -369,6 +365,9 @@ static void indirect(void *obj, void *u_data, QGuestAllocator *t_alloc)
                             (1u << VIRTIO_BLK_F_SCSI));
     qvirtio_set_features(dev, features);
 
+    capacity = qvirtio_config_readq(dev, 0);
+    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
+
     vq = qvirtqueue_setup(dev, t_alloc, 0);
     qvirtio_set_driver_ok(dev);
 
@@ -434,8 +433,16 @@ static void config(void *obj, void *data, QGuestAllocator *t_alloc)
     QVirtioBlk *blk_if = obj;
     QVirtioDevice *dev = blk_if->vdev;
     int n_size = TEST_IMAGE_SIZE / 2;
+    uint64_t features;
     uint64_t capacity;
 
+    features = qvirtio_get_features(dev);
+    features = features & ~(QVIRTIO_F_BAD_FEATURE |
+                            (1u << VIRTIO_RING_F_INDIRECT_DESC) |
+                            (1u << VIRTIO_RING_F_EVENT_IDX) |
+                            (1u << VIRTIO_BLK_F_SCSI));
+    qvirtio_set_features(dev, features);
+
     capacity = qvirtio_config_readq(dev, 0);
     g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
 
@@ -475,9 +482,6 @@ static void msix(void *obj, void *u_data, QGuestAllocator *t_alloc)
     qpci_msix_enable(pdev->pdev);
     qvirtio_pci_set_msix_configuration_vector(pdev, t_alloc, 0);
 
-    capacity = qvirtio_config_readq(dev, 0);
-    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
-
     features = qvirtio_get_features(dev);
     features = features & ~(QVIRTIO_F_BAD_FEATURE |
                             (1u << VIRTIO_RING_F_INDIRECT_DESC) |
@@ -485,6 +489,9 @@ static void msix(void *obj, void *u_data, QGuestAllocator *t_alloc)
                             (1u << VIRTIO_BLK_F_SCSI));
     qvirtio_set_features(dev, features);
 
+    capacity = qvirtio_config_readq(dev, 0);
+    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
+
     vq = qvirtqueue_setup(dev, t_alloc, 0);
     qvirtqueue_pci_msix_setup(pdev, (QVirtQueuePCI *)vq, t_alloc, 1);
 
@@ -584,9 +591,6 @@ static void idx(void *obj, void *u_data, QGuestAllocator *t_alloc)
     qpci_msix_enable(pdev->pdev);
     qvirtio_pci_set_msix_configuration_vector(pdev, t_alloc, 0);
 
-    capacity = qvirtio_config_readq(dev, 0);
-    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
-
     features = qvirtio_get_features(dev);
     features = features & ~(QVIRTIO_F_BAD_FEATURE |
                             (1u << VIRTIO_RING_F_INDIRECT_DESC) |
@@ -594,6 +598,9 @@ static void idx(void *obj, void *u_data, QGuestAllocator *t_alloc)
                             (1u << VIRTIO_BLK_F_SCSI));
     qvirtio_set_features(dev, features);
 
+    capacity = qvirtio_config_readq(dev, 0);
+    g_assert_cmpint(capacity, ==, TEST_IMAGE_SIZE / 512);
+
     vq = qvirtqueue_setup(dev, t_alloc, 0);
     qvirtqueue_pci_msix_setup(pdev, (QVirtQueuePCI *)vq, t_alloc, 1);
 
-- 
2.21.0

On 19/10/2019 08.37, Stefan Hajnoczi wrote:
> The VIRTIO Configuration Space cannot be accessed before device feature
> bits have been read because a driver doesn't know the endianness until
> it has checked VIRTIO_F_VERSION_1.
> 
> Fix this problem in preparation for VIRTIO 1.0 support.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tests/virtio-blk-test.c | 33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)

Reviewed-by: Thomas Huth <thuth@redhat.com>