From: Jean-Philippe Brucker <jean-philippe@linaro.org>

We do not support instantiating multiple IOMMUs. Before adding a
virtio-iommu, check that no other IOMMU is present. This will detect
both "iommu=smmuv3" machine parameter and another virtio-iommu instance.

Fixes: 70e89132c9 ("hw/arm/virt: Add the virtio-iommu device tree mappings")
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-id: 20211210170415.583179-4-jean-philippe@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/arm/virt.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index e621cada990..41c9808a3fd 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2493,6 +2493,11 @@ static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
         hwaddr db_start = 0, db_end = 0;
         char *resv_prop_str;
 
+        if (vms->iommu != VIRT_IOMMU_NONE) {
+            error_setg(errp, "virt machine does not support multiple IOMMUs");
+            return;
+        }
+
         switch (vms->msi_controller) {
         case VIRT_MSI_CTRL_NONE:
             return;
-- 
2.25.1