1 files changed, 46 insertions, 22 deletions

diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index 0b92fcf859..23f667ef4b 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -25,15 +25,30 @@
 
 /* vring_map can be coupled with vring_unmap or (if you still have the
  * value returned in *mr) memory_region_unref.
+ * Returns NULL on failure.
+ * Callers that can handle a partial mapping must supply mapped_len pointer to
+ * get the actual length mapped.
+ * Passing mapped_len == NULL requires either a full mapping or a failure.
  */
-static void *vring_map(MemoryRegion **mr, hwaddr phys, hwaddr len,
+static void *vring_map(MemoryRegion **mr, hwaddr phys,
+                       hwaddr len, hwaddr *mapped_len,
                        bool is_write)
 {
     MemoryRegionSection section = memory_region_find(get_system_memory(), phys, len);
+    uint64_t size;
 
-    if (!section.mr || int128_get64(section.size) < len) {
+    if (!section.mr) {
         goto out;
     }
+
+    size = int128_get64(section.size);
+    assert(size);
+
+    /* Passing mapped_len == NULL requires either a full mapping or a failure. */
+    if (!mapped_len && size < len) {
+        goto out;
+    }
+
     if (is_write && section.readonly) {
         goto out;
     }
@@ -46,6 +61,10 @@ static void *vring_map(MemoryRegion **mr, hwaddr phys, hwaddr len,
         goto out;
     }
 
+    if (mapped_len) {
+        *mapped_len = MIN(size, len);
+    }
+
     *mr = section.mr;
     return memory_region_get_ram_ptr(section.mr) + section.offset_within_region;
 
@@ -78,7 +97,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
     addr = virtio_queue_get_desc_addr(vdev, n);
     size = virtio_queue_get_desc_size(vdev, n);
     /* Map the descriptor area as read only */
-    ptr = vring_map(&vring->mr_desc, addr, size, false);
+    ptr = vring_map(&vring->mr_desc, addr, size, NULL, false);
     if (!ptr) {
         error_report("Failed to map 0x%" HWADDR_PRIx " byte for vring desc "
                      "at 0x%" HWADDR_PRIx,
@@ -92,7 +111,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
     /* Add the size of the used_event_idx */
     size += sizeof(uint16_t);
     /* Map the driver area as read only */
-    ptr = vring_map(&vring->mr_avail, addr, size, false);
+    ptr = vring_map(&vring->mr_avail, addr, size, NULL, false);
     if (!ptr) {
         error_report("Failed to map 0x%" HWADDR_PRIx " byte for vring avail "
                      "at 0x%" HWADDR_PRIx,
@@ -106,7 +125,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
     /* Add the size of the avail_event_idx */
     size += sizeof(uint16_t);
     /* Map the device area as read-write */
-    ptr = vring_map(&vring->mr_used, addr, size, true);
+    ptr = vring_map(&vring->mr_used, addr, size, NULL, true);
     if (!ptr) {
         error_report("Failed to map 0x%" HWADDR_PRIx " byte for vring used "
                      "at 0x%" HWADDR_PRIx,
@@ -206,6 +225,7 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
     struct iovec *iov;
     hwaddr *addr;
     MemoryRegion *mr;
+    hwaddr len;
 
     if (desc->flags & VRING_DESC_F_WRITE) {
         num = &elem->in_num;
@@ -224,26 +244,30 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
         }
     }
 
-    /* Stop for now if there are not enough iovecs available. */
-    if (*num >= VIRTQUEUE_MAX_SIZE) {
-        error_report("Invalid SG num: %u", *num);
-        return -EFAULT;
-    }
+    while (desc->len) {
+        /* Stop for now if there are not enough iovecs available. */
+        if (*num >= VIRTQUEUE_MAX_SIZE) {
+            error_report("Invalid SG num: %u", *num);
+            return -EFAULT;
+        }
 
-    /* TODO handle non-contiguous memory across region boundaries */
-    iov->iov_base = vring_map(&mr, desc->addr, desc->len,
-                              desc->flags & VRING_DESC_F_WRITE);
-    if (!iov->iov_base) {
-        error_report("Failed to map descriptor addr %#" PRIx64 " len %u",
-                     (uint64_t)desc->addr, desc->len);
-        return -EFAULT;
+        iov->iov_base = vring_map(&mr, desc->addr, desc->len, &len,
+                                  desc->flags & VRING_DESC_F_WRITE);
+        if (!iov->iov_base) {
+            error_report("Failed to map descriptor addr %#" PRIx64 " len %u",
+                         (uint64_t)desc->addr, desc->len);
+            return -EFAULT;
+        }
+
+        /* The MemoryRegion is looked up again and unref'ed later, leave the
+         * ref in place.  */
+        (iov++)->iov_len = len;
+        *addr++ = desc->addr;
+        desc->len -= len;
+        desc->addr += len;
+        *num += 1;
     }
 
-    /* The MemoryRegion is looked up again and unref'ed later, leave the
-     * ref in place.  */
-    iov->iov_len = desc->len;
-    *addr = desc->addr;
-    *num += 1;
     return 0;
 }