From: Prasad J Pandit <pjp@fedoraproject.org>

An uninitialised VirtQueue object or one with Vring.align field
set to zero(0) could lead to arithmetic exceptions. Add a unit
test to validate it.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 tests/virtio-blk-test.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tests/virtio-blk-test.c b/tests/virtio-blk-test.c
index e6fb9bac87..d00ceb0501 100644
--- a/tests/virtio-blk-test.c
+++ b/tests/virtio-blk-test.c
@@ -674,6 +674,26 @@ static void pci_hotplug(void)
     qtest_shutdown(qs);
 }
 
+static void test_vring_align(void)
+{
+    QPCIBar bar0;
+    QOSState *qs;
+    QPCIDevice *dev;
+
+    qs = pci_test_start();
+    dev = qpci_device_find(qs->pcibus, QPCI_DEVFN(4, 0));
+    g_assert(dev != NULL);
+
+    qpci_device_enable(dev);
+    bar0 = qpci_iomap(dev, 0, NULL);
+
+    qpci_io_writeb(dev, bar0, VIRTIO_PCI_QUEUE_SEL, 2);
+    qpci_io_writel(dev, bar0, VIRTIO_PCI_QUEUE_PFN, 1);
+
+    g_free(dev);
+    qtest_shutdown(qs);
+}
+
 static void mmio_basic(void)
 {
     QVirtioMMIODevice *dev;
@@ -724,6 +744,7 @@ int main(int argc, char **argv)
         qtest_add_func("/virtio/blk/pci/basic", pci_basic);
         qtest_add_func("/virtio/blk/pci/indirect", pci_indirect);
         qtest_add_func("/virtio/blk/pci/config", pci_config);
+        qtest_add_func("/virtio/blk/pci/vring", test_vring_align);
         if (strcmp(arch, "i386") == 0 || strcmp(arch, "x86_64") == 0) {
             qtest_add_func("/virtio/blk/pci/msix", pci_msix);
             qtest_add_func("/virtio/blk/pci/idx", pci_idx);
-- 
2.13.6

On Fri, Nov 24, 2017 at 01:25:42PM +0530, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> An uninitialised VirtQueue object or one with Vring.align field
> set to zero(0) could lead to arithmetic exceptions. Add a unit
> test to validate it.
> 
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  tests/virtio-blk-test.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/tests/virtio-blk-test.c b/tests/virtio-blk-test.c
> index e6fb9bac87..d00ceb0501 100644
> --- a/tests/virtio-blk-test.c
> +++ b/tests/virtio-blk-test.c
> @@ -674,6 +674,26 @@ static void pci_hotplug(void)
>      qtest_shutdown(qs);
>  }
>  
> +static void test_vring_align(void)

It's important to include a doc comment so the purpose of the test is
clear:

/*
 * Check that setting the vring addr on a non-existent virtqueue does
 * not crash.
 */

I think the _align name is confusing since the vring alignment is not
directly affected by this test case.  Please call it
test_nonexistent_virtqueue() instead.

> +{
> +    QPCIBar bar0;
> +    QOSState *qs;
> +    QPCIDevice *dev;
> +
> +    qs = pci_test_start();
> +    dev = qpci_device_find(qs->pcibus, QPCI_DEVFN(4, 0));
> +    g_assert(dev != NULL);
> +
> +    qpci_device_enable(dev);
> +    bar0 = qpci_iomap(dev, 0, NULL);
> +
> +    qpci_io_writeb(dev, bar0, VIRTIO_PCI_QUEUE_SEL, 2);
> +    qpci_io_writel(dev, bar0, VIRTIO_PCI_QUEUE_PFN, 1);
> +
> +    g_free(dev);
> +    qtest_shutdown(qs);
> +}