[PATCH v2] hw/vfio/common: Trace in which mode an IOMMU is opened

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

One might want to check which IOMMU version the host kernel
provide. Add a trace event to see in which mode we opened
our container.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: Only display string description (Eric)

Supersedes: <20200526173542.28710-1-philmd@redhat.com>
---
 hw/vfio/common.c     | 19 ++++++++++++++-----
 hw/vfio/trace-events |  1 +
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 0b3593b3c0..f24450472e 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1157,15 +1157,24 @@ static void vfio_put_address_space(VFIOAddressSpace *space)
 static int vfio_get_iommu_type(VFIOContainer *container,
                                Error **errp)
 {
-    int iommu_types[] = { VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
-                          VFIO_SPAPR_TCE_v2_IOMMU, VFIO_SPAPR_TCE_IOMMU };
+    static const struct {
+        int type;
+        const char *name;
+    } iommu[] = {
+        {VFIO_TYPE1v2_IOMMU, "Type1 (v2)"},
+        {VFIO_TYPE1_IOMMU, "Type1 (v1)"},
+        {VFIO_SPAPR_TCE_v2_IOMMU, "sPAPR TCE (v2)"},
+        {VFIO_SPAPR_TCE_IOMMU, "sPAPR TCE (v1)"}
+    };
     int i;
 
-    for (i = 0; i < ARRAY_SIZE(iommu_types); i++) {
-        if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu_types[i])) {
-            return iommu_types[i];
+    for (i = 0; i < ARRAY_SIZE(iommu); i++) {
+        if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu[i].type)) {
+            trace_vfio_get_iommu_type(iommu[i].name);
+            return iommu[i].type;
         }
     }
+    trace_vfio_get_iommu_type("Not available or not supported");
     error_setg(errp, "No available IOMMU models");
     return -EINVAL;
 }
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index b1ef55a33f..d3f1e48618 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -115,6 +115,7 @@ vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Devic
 vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
 vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
 vfio_dma_unmap_overflow_workaround(void) ""
+vfio_get_iommu_type(const char *type) "IOMMU type: %s"
 
 # platform.c
 vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"
-- 
2.21.3