[Qemu-devel] [PATCH v2] virtio-pci: error out when both legacy and modern modes are disabled

[Greg Kurz]

From: Greg Kurz <address@hidden>

Without presuming if we got there because of a user mistake or some
more subtle bug in the tooling, it really does not make sense to
implement a non-functional device.

Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Marcel Apfelbaum <address@hidden>
Reviewed-by: Cornelia Huck <address@hidden>
Signed-off-by: Greg Kurz <address@hidden>
---
v2: - moved the check to virtio_pci_realize() to ensure disable_legacy is
      either ON or OFF, but not AUTO (this would cause the check to fail
      before we have a chance to know if the device can actually work).

I've kept the R-b tags, please raise a flag if this is inapropriate.

I've dropped the other patch about virtio-9p: the issue will be addressed
in a separate series.
---
 hw/virtio/virtio-pci.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 268fd8ebb219..551c4346bf4b 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1770,6 +1770,14 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error 
**errp)
         proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
     }
 
+    if (!(virtio_pci_modern(proxy) || virtio_pci_legacy(proxy))) {
+        error_setg(errp, "device cannot work as neither modern nor legacy mode"
+                   " is enabled");
+        error_append_hint(errp, "Set either disable-modern or disable-legacy"
+                          " to off\n");
+        return;
+    }
+
     if (pcie_port && pci_is_express(pci_dev)) {
         int pos;