virtio-iommu: Support bypass domain

The driver can create a bypass domain by passing the
VIRTIO_IOMMU_ATTACH_F_BYPASS flag on the ATTACH request. Bypass domains
perform slightly better than domains with identity mappings since they
skip translation.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-Id: <20220214124356.872985-4-jean-philippe@linaro.org>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/virtio/virtio-iommu.c

@@ -43,6 +43,7 @@
 
 typedef struct VirtIOIOMMUDomain {
     uint32_t id;
+    bool bypass;
     GTree *mappings;
     QLIST_HEAD(, VirtIOIOMMUEndpoint) endpoint_list;
 } VirtIOIOMMUDomain;
@@ -258,12 +259,16 @@ static void virtio_iommu_put_endpoint(gpointer data)
 }
 
 static VirtIOIOMMUDomain *virtio_iommu_get_domain(VirtIOIOMMU *s,
-                                                  uint32_t domain_id)
+                                                  uint32_t domain_id,
+                                                  bool bypass)
 {
     VirtIOIOMMUDomain *domain;
 
     domain = g_tree_lookup(s->domains, GUINT_TO_POINTER(domain_id));
     if (domain) {
+        if (domain->bypass != bypass) {
+            return NULL;
+        }
         return domain;
     }
     domain = g_malloc0(sizeof(*domain));
@@ -271,6 +276,7 @@ static VirtIOIOMMUDomain *virtio_iommu_get_domain(VirtIOIOMMU *s,
     domain->mappings = g_tree_new_full((GCompareDataFunc)interval_cmp,
                                    NULL, (GDestroyNotify)g_free,
                                    (GDestroyNotify)g_free);
+    domain->bypass = bypass;
     g_tree_insert(s->domains, GUINT_TO_POINTER(domain_id), domain);
     QLIST_INIT(&domain->endpoint_list);
     trace_virtio_iommu_get_domain(domain_id);
@@ -334,11 +340,16 @@ static int virtio_iommu_attach(VirtIOIOMMU *s,
 {
     uint32_t domain_id = le32_to_cpu(req->domain);
     uint32_t ep_id = le32_to_cpu(req->endpoint);
+    uint32_t flags = le32_to_cpu(req->flags);
     VirtIOIOMMUDomain *domain;
     VirtIOIOMMUEndpoint *ep;
 
     trace_virtio_iommu_attach(domain_id, ep_id);
 
+    if (flags & ~VIRTIO_IOMMU_ATTACH_F_BYPASS) {
+        return VIRTIO_IOMMU_S_INVAL;
+    }
+
     ep = virtio_iommu_get_endpoint(s, ep_id);
     if (!ep) {
         return VIRTIO_IOMMU_S_NOENT;
@@ -356,7 +367,12 @@ static int virtio_iommu_attach(VirtIOIOMMU *s,
         }
     }
 
-    domain = virtio_iommu_get_domain(s, domain_id);
+    domain = virtio_iommu_get_domain(s, domain_id,
+                                     flags & VIRTIO_IOMMU_ATTACH_F_BYPASS);
+    if (!domain) {
+        /* Incompatible bypass flag */
+        return VIRTIO_IOMMU_S_INVAL;
+    }
     QLIST_INSERT_HEAD(&domain->endpoint_list, ep, next);
 
     ep->domain = domain;
@@ -419,6 +435,10 @@ static int virtio_iommu_map(VirtIOIOMMU *s,
         return VIRTIO_IOMMU_S_NOENT;
     }
 
+    if (domain->bypass) {
+        return VIRTIO_IOMMU_S_INVAL;
+    }
+
     interval = g_malloc0(sizeof(*interval));
 
     interval->low = virt_start;
@@ -464,6 +484,11 @@ static int virtio_iommu_unmap(VirtIOIOMMU *s,
     if (!domain) {
         return VIRTIO_IOMMU_S_NOENT;
     }
+
+    if (domain->bypass) {
+        return VIRTIO_IOMMU_S_INVAL;
+    }
+
     interval.low = virt_start;
     interval.high = virt_end;
 
@@ -780,6 +805,9 @@ static IOMMUTLBEntry virtio_iommu_translate(IOMMUMemoryRegion *mr, hwaddr addr,
             entry.perm = flag;
         }
         goto unlock;
+    } else if (ep->domain->bypass) {
+        entry.perm = flag;
+        goto unlock;
     }
 
     found = g_tree_lookup_extended(ep->domain->mappings, (gpointer)(&interval),
@@ -1139,8 +1167,8 @@ static const VMStateDescription vmstate_endpoint = {
 
 static const VMStateDescription vmstate_domain = {
     .name = "domain",
-    .version_id = 1,
+    .version_id = 2,
-    .minimum_version_id = 1,
+    .minimum_version_id = 2,
     .pre_load = domain_preload,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(id, VirtIOIOMMUDomain),
@@ -1149,6 +1177,7 @@ static const VMStateDescription vmstate_domain = {
                         VirtIOIOMMUInterval, VirtIOIOMMUMapping),
         VMSTATE_QLIST_V(endpoint_list, VirtIOIOMMUDomain, 1,
                         vmstate_endpoint, VirtIOIOMMUEndpoint, next),
+        VMSTATE_BOOL_V(bypass, VirtIOIOMMUDomain, 2),
         VMSTATE_END_OF_LIST()
     }
 };
@@ -1186,7 +1215,7 @@ static const VMStateDescription vmstate_virtio_iommu_device = {
     .version_id = 2,
     .post_load = iommu_post_load,
     .fields = (VMStateField[]) {
-        VMSTATE_GTREE_DIRECT_KEY_V(domains, VirtIOIOMMU, 1,
+        VMSTATE_GTREE_DIRECT_KEY_V(domains, VirtIOIOMMU, 2,
                                    &vmstate_domain, VirtIOIOMMUDomain),
         VMSTATE_UINT8_V(config.bypass, VirtIOIOMMU, 2),
         VMSTATE_END_OF_LIST()