virtio-gpu: handle partial maps properly

dma_memory_map() may map only a part of the request.  Happens if the
request can't be mapped in one go, for example due to a iommu creating
a linear dma mapping for scattered physical pages.  Should that be the
case virtio-gpu must call dma_memory_map() again with the remaining
range instead of simply throwing an error.

Note that this change implies the number of iov entries may differ from
the number of mapping entries sent by the guest.  Therefore the iov_len
bookkeeping needs some updates too, we have to explicitly pass around
the iov length now.

Reported-by: Auger Eric <eric.auger@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20210506091001.1301250-1-kraxel@redhat.com
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20210506091001.1301250-1-kraxel@redhat.com>

2 files changed, 50 insertions, 33 deletions

diff --git a/hw/display/virtio-gpu-3d.c b/hw/display/virtio-gpu-3d.c
index d989648..72c14d9 100644
--- a/hw/display/virtio-gpu-3d.c
+++ b/hw/display/virtio-gpu-3d.c
@@ -283,22 +283,23 @@ static void virgl_resource_attach_backing(VirtIOGPU *g,
 {
     struct virtio_gpu_resource_attach_backing att_rb;
     struct iovec *res_iovs;
+    uint32_t res_niov;
     int ret;
 
     VIRTIO_GPU_FILL_CMD(att_rb);
     trace_virtio_gpu_cmd_res_back_attach(att_rb.resource_id);
 
-    ret = virtio_gpu_create_mapping_iov(g, &att_rb, cmd, NULL, &res_iovs);
+    ret = virtio_gpu_create_mapping_iov(g, &att_rb, cmd, NULL, &res_iovs, &res_niov);
     if (ret != 0) {
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         return;
     }
 
     ret = virgl_renderer_resource_attach_iov(att_rb.resource_id,
-                                             res_iovs, att_rb.nr_entries);
+                                             res_iovs, res_niov);
 
     if (ret != 0)
-        virtio_gpu_cleanup_mapping_iov(g, res_iovs, att_rb.nr_entries);
+        virtio_gpu_cleanup_mapping_iov(g, res_iovs, res_niov);
 }
 
 static void virgl_resource_detach_backing(VirtIOGPU *g,
diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index c9f5e36..6f3791d 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -608,11 +608,12 @@ static void virtio_gpu_set_scanout(VirtIOGPU *g,
 int virtio_gpu_create_mapping_iov(VirtIOGPU *g,
                                   struct virtio_gpu_resource_attach_backing *ab,
                                   struct virtio_gpu_ctrl_command *cmd,
-                                  uint64_t **addr, struct iovec **iov)
+                                  uint64_t **addr, struct iovec **iov,
+                                  uint32_t *niov)
 {
     struct virtio_gpu_mem_entry *ents;
     size_t esize, s;
-    int i;
+    int e, v;
 
     if (ab->nr_entries > 16384) {
         qemu_log_mask(LOG_GUEST_ERROR,
@@ -633,37 +634,53 @@ int virtio_gpu_create_mapping_iov(VirtIOGPU *g,
         return -1;
     }
 
-    *iov = g_malloc0(sizeof(struct iovec) * ab->nr_entries);
+    *iov = NULL;
     if (addr) {
-        *addr = g_malloc0(sizeof(uint64_t) * ab->nr_entries);
+        *addr = NULL;
     }
-    for (i = 0; i < ab->nr_entries; i++) {
-        uint64_t a = le64_to_cpu(ents[i].addr);
-        uint32_t l = le32_to_cpu(ents[i].length);
-        hwaddr len = l;
-        (*iov)[i].iov_base = dma_memory_map(VIRTIO_DEVICE(g)->dma_as,
-                                            a, &len, DMA_DIRECTION_TO_DEVICE);
-        (*iov)[i].iov_len = len;
-        if (addr) {
-            (*addr)[i] = a;
-        }
-        if (!(*iov)[i].iov_base || len != l) {
-            qemu_log_mask(LOG_GUEST_ERROR, "%s: failed to map MMIO memory for"
-                          " resource %d element %d\n",
-                          __func__, ab->resource_id, i);
-            if ((*iov)[i].iov_base) {
-                i++; /* cleanup the 'i'th map */
+    for (e = 0, v = 0; e < ab->nr_entries; e++) {
+        uint64_t a = le64_to_cpu(ents[e].addr);
+        uint32_t l = le32_to_cpu(ents[e].length);
+        hwaddr len;
+        void *map;
+
+        do {
+            len = l;
+            map = dma_memory_map(VIRTIO_DEVICE(g)->dma_as,
+                                 a, &len, DMA_DIRECTION_TO_DEVICE);
+            if (!map) {
+                qemu_log_mask(LOG_GUEST_ERROR, "%s: failed to map MMIO memory for"
+                              " resource %d element %d\n",
+                              __func__, ab->resource_id, e);
+                virtio_gpu_cleanup_mapping_iov(g, *iov, v);
+                g_free(ents);
+                *iov = NULL;
+                if (addr) {
+                    g_free(*addr);
+                    *addr = NULL;
+                }
+                return -1;
+            }
+
+            if (!(v % 16)) {
+                *iov = g_realloc(*iov, sizeof(struct iovec) * (v + 16));
+                if (addr) {
+                    *addr = g_realloc(*addr, sizeof(uint64_t) * (v + 16));
+                }
             }
-            virtio_gpu_cleanup_mapping_iov(g, *iov, i);
-            g_free(ents);
-            *iov = NULL;
+            (*iov)[v].iov_base = map;
+            (*iov)[v].iov_len = len;
             if (addr) {
-                g_free(*addr);
-                *addr = NULL;
+                (*addr)[v] = a;
             }
-            return -1;
-        }
+
+            a += len;
+            l -= len;
+            v += 1;
+        } while (l > 0);
     }
+    *niov = v;
+
     g_free(ents);
     return 0;
 }
@@ -717,13 +734,12 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
         return;
     }
 
-    ret = virtio_gpu_create_mapping_iov(g, &ab, cmd, &res->addrs, &res->iov);
+    ret = virtio_gpu_create_mapping_iov(g, &ab, cmd, &res->addrs,
+                                        &res->iov, &res->iov_cnt);
     if (ret != 0) {
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         return;
     }
-
-    res->iov_cnt = ab.nr_entries;
 }
 
 static void