[Qemu-devel] [PATCH 1/4] introduce virtqueue_unmap_sg

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Introduce a function to unmap an sg previously mapped with
virtqueue_map_sg.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: jasowang@redhat.com
CC: wency@cn.fujitsu.com
CC: mst@redhat.com
CC: pbonzini@redhat.com
---
 hw/virtio/virtio.c         |   22 ++++++++++++++++++++++
 include/hw/virtio/virtio.h |    2 ++
 2 files changed, 24 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 3e4b70c..2621ae6 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -446,6 +446,28 @@ void virtqueue_map_sg(struct iovec *sg, hwaddr *addr,
     }
 }
 
+void virtqueue_unmap_sg(const struct iovec *sg, size_t num_sg,
+                        int is_write, unsigned int len)
+{
+    unsigned int i;
+    unsigned int offset;
+
+    if (num_sg > VIRTQUEUE_MAX_SIZE) {
+        error_report("virtio: unmap attempt out of bounds: %zd > %d",
+                     num_sg, VIRTQUEUE_MAX_SIZE);
+        exit(1);
+    }
+
+    offset = 0;
+    for (i = 0; i < num_sg; i++) {
+        size_t size = MIN(len - offset, sg[i].iov_len);
+
+        cpu_physical_memory_unmap(sg[i].iov_base, sg[i].iov_len, is_write, size);
+
+        offset += size;
+    }
+}
+
 int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
 {
     unsigned int i, head, max;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 3e54e90..2325053 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -173,6 +173,8 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
 
 void virtqueue_map_sg(struct iovec *sg, hwaddr *addr,
     size_t num_sg, int is_write);
+void virtqueue_unmap_sg(const struct iovec *sg, size_t num_sg,
+                        int is_write, unsigned int len);
 int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem);
 int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
                           unsigned int out_bytes);
-- 
1.7.10.4