[PATCH 5/5] vfio: Check compatibility of CPU and IOMMU address space width

[Cédric Le Goater]

Print a warning if IOMMU address space width is smaller than the
physical address width. In this case, PCI peer-to-peer transactions on
BARs are not supported and failures of device MMIO regions are to be
expected.

This can occur with the 39-bit IOMMU address space width as found on
consumer grade processors or when using a vIOMMU device with default
settings.

Signed-off-by: Cédric Le Goater <c...@redhat.com>
---
 hw/vfio/common.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 
561be7f57cf903e6e2bcbbb708be9e4d4ee8941c..d0104976e9d99c3f64ec716accd3adb4a70d9afe
 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -44,6 +44,8 @@
 #include "migration/qemu-file.h"
 #include "system/tpm.h"
 
+#include "hw/core/cpu.h"
+
 VFIODeviceList vfio_device_list =
     QLIST_HEAD_INITIALIZER(vfio_device_list);
 static QLIST_HEAD(, VFIOAddressSpace) vfio_address_spaces =
@@ -1561,12 +1563,28 @@ retry:
     return info;
 }
 
+static bool vfio_device_check_address_space(VFIODevice *vbasedev, Error **errp)
+{
+    uint32_t cpu_aw_bits = cpu_get_phys_bits(first_cpu);
+    uint32_t iommu_aw_bits = vfio_device_get_aw_bits(vbasedev);
+
+    if (cpu_aw_bits && cpu_aw_bits > iommu_aw_bits) {
+        error_setg(errp, "Host physical address space (%u) is larger than "
+                   "the host IOMMU address space (%u).", cpu_aw_bits,
+                   iommu_aw_bits);
+        vfio_container_p2p_error_append(vbasedev->bcontainer, errp);
+        return false;
+    }
+    return true;
+}
+
 bool vfio_attach_device(char *name, VFIODevice *vbasedev,
                         AddressSpace *as, Error **errp)
 {
     const VFIOIOMMUClass *ops =
         VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_LEGACY));
     HostIOMMUDevice *hiod = NULL;
+    Error *local_err = NULL;
 
     if (vbasedev->iommufd) {
         ops = VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_IOMMUFD));
@@ -1586,6 +1604,9 @@ bool vfio_attach_device(char *name, VFIODevice *vbasedev,
         return false;
     }
 
+    if (!vfio_device_check_address_space(vbasedev, &local_err)) {
+        warn_report_err(local_err);
+    }
     return true;
 }
 
-- 
2.48.1