hw/arm/virt: Let the virtio-iommu bypass MSIs

At the moment the virtio-iommu translates MSI transactions.
This behavior is inherited from ARM SMMU. The virt machine
code knows where the guest MSI doorbells are so we can easily
declare those regions as VIRTIO_IOMMU_RESV_MEM_T_MSI. With that
setting the guest will not map MSIs through the IOMMU and those
transactions will be simply bypassed.

Depending on which MSI controller is in use (ITS or GICV2M),
we declare either:
- the ITS interrupt translation space (ITS_base + 0x10000),
  containing the GITS_TRANSLATOR or
- The GICV2M single frame, containing the MSI_SETSP_NS register.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20200629070404.10969-6-eric.auger@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index af3050bc4b..7922f3c23a 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -600,6 +600,7 @@ static void create_its(VirtMachineState *vms)
     sysbus_mmio_map(SYS_BUS_DEVICE(dev), 0, vms->memmap[VIRT_GIC_ITS].base);
 
     fdt_add_its_gic_node(vms);
+    vms->msi_controller = VIRT_MSI_CTRL_ITS;
 }
 
 static void create_v2m(VirtMachineState *vms)
@@ -620,6 +621,7 @@ static void create_v2m(VirtMachineState *vms)
     }
 
     fdt_add_v2m_gic_node(vms);
+    vms->msi_controller = VIRT_MSI_CTRL_GICV2M;
 }
 
 static void create_gic(VirtMachineState *vms)
@@ -2198,8 +2200,36 @@ out:
 static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
                                             DeviceState *dev, Error **errp)
 {
+    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
+
     if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
         virt_memory_pre_plug(hotplug_dev, dev, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
+        hwaddr db_start = 0, db_end = 0;
+        char *resv_prop_str;
+
+        switch (vms->msi_controller) {
+        case VIRT_MSI_CTRL_NONE:
+            return;
+        case VIRT_MSI_CTRL_ITS:
+            /* GITS_TRANSLATER page */
+            db_start = base_memmap[VIRT_GIC_ITS].base + 0x10000;
+            db_end = base_memmap[VIRT_GIC_ITS].base +
+                     base_memmap[VIRT_GIC_ITS].size - 1;
+            break;
+        case VIRT_MSI_CTRL_GICV2M:
+            /* MSI_SETSPI_NS page */
+            db_start = base_memmap[VIRT_GIC_V2M].base;
+            db_end = db_start + base_memmap[VIRT_GIC_V2M].size - 1;
+            break;
+        }
+        resv_prop_str = g_strdup_printf("0x%"PRIx64":0x%"PRIx64":%u",
+                                        db_start, db_end,
+                                        VIRTIO_IOMMU_RESV_MEM_T_MSI);
+
+        qdev_prop_set_uint32(dev, "len-reserved-regions", 1);
+        qdev_prop_set_string(dev, "reserved-regions[0]", resv_prop_str);
+        g_free(resv_prop_str);
     }
 }