@@ -78,3 +78,4 @@ subdir-$(CONFIG_UBSAN) += ubsan
subdir-$(CONFIG_NEEDS_LIBELF) += libelf
subdir-$(CONFIG_HAS_DEVICE_TREE) += libfdt
+subdir-y += lu
new file mode 100644
@@ -0,0 +1 @@
+obj-y += stream.o
new file mode 100644
@@ -0,0 +1,108 @@
+/*
+ * Live update data stream handling.
+ *
+ * During live update, one version of Xen (Xen#1) performs a kexec into
+ * a new version of Xen (Xen#2), performing guest-transparent live
+ * migration of all existing domains.
+ *
+ * Xen#2 must avoid scribbling on any pages which may belong to existing
+ * domains. In order to achieve this, we reserve a contiguous area of
+ * physical memory to be used by the boot allocator in Xen#2. Xen must
+ * not allocate pages from that region which are later shared with
+ * guests or need to persist across live update.
+ *
+ * The live update bootmem region is reserved by the first Xen to boot,
+ * and userspace can obtain its address using KEXEC_CMD_kexec_get_range
+ * with the new KEXEC_RANGE_MA_LIVEUPDATE type. Userspace kexec(8)
+ * appends the appropriate 'liveupdate=' parameter to the command line
+ * of Xen#2 when setting up the kexec image.
+ *
+ * At the time of kexec, Xen#1 serialises the domain state into buffers
+ * allocated from its own heap., then creates a single physically
+ * contiguous scatter-gather list containing the MFNs of those data
+ * pages (which Xen#2 can then trivially vmap()). In a system with
+ * 4KiB pages, the MFN list for the live update data stream will fit
+ * into a single page until the total size of the live update data
+ * exceeds 2MiB.
+ *
+ * The physical address of the MFN list is passed to Xen#2 by placing
+ * it at the start of the reserved live update bootmem region, with a
+ * magic number to avoid false positives.
+ */
+
+#include <xen/types.h>
+#include <xen/vmap.h>
+#include <xen/lu.h>
+
+static int lu_stream_extend(struct lu_stream *stream, int nr_pages)
+{
+ int order = get_order_from_bytes((nr_pages + 1) * sizeof(mfn_t));
+ int old_order = get_order_from_bytes((stream->nr_pages + 1) * sizeof(mfn_t));
+
+ if (!stream->nr_pages || order > old_order) {
+ mfn_t *new_pglist = alloc_xenheap_pages(order, 0);
+ if (!new_pglist)
+ return -ENOMEM;
+
+ if (stream->nr_pages) {
+ memcpy(new_pglist, stream->pagelist,
+ stream->nr_pages * sizeof(mfn_t));
+ free_xenheap_pages(stream->pagelist, old_order);
+ }
+ stream->pagelist = new_pglist;
+ }
+ while (stream->nr_pages < nr_pages) {
+ struct page_info *pg = alloc_domheap_page(NULL, MEMF_no_owner);
+ if (!pg) {
+ /* Ensure the cleanup frees the correct order of pagelist */
+ stream->nr_pages++;
+ return -ENOMEM;
+ }
+ stream->pagelist[stream->nr_pages++] = page_to_mfn(pg);
+ stream->pagelist[stream->nr_pages] = 0;
+ }
+
+ if (stream->data)
+ vunmap(stream->data);
+ stream->data = vmap(stream->pagelist, stream->nr_pages);
+ if (!stream->data)
+ return -ENOMEM;
+
+ return 0;
+}
+
+void *lu_stream_reserve(struct lu_stream *stream, size_t size)
+{
+ int nr_pages = (stream->len + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+ if (stream->nr_pages < nr_pages && lu_stream_extend(stream, nr_pages))
+ return NULL;
+
+ return stream->data + stream->len;
+}
+
+void lu_stream_end_reservation(struct lu_stream *stream, size_t size)
+{
+ stream->len += size;
+}
+
+int lu_stream_append(struct lu_stream *stream, void *data, size_t size)
+{
+ void *p = lu_stream_reserve(stream, size);
+ if (!p)
+ return -ENOMEM;
+ memcpy(p, data, size);
+ lu_stream_end_reservation(stream, size);
+
+ return 0;
+}
+
+void lu_stream_free(struct lu_stream *stream)
+{
+ int order = get_order_from_bytes((stream->nr_pages + 1) * sizeof(mfn_t));
+
+ if (stream->pagelist)
+ free_xenheap_pages(stream->pagelist, order);
+ if (stream->data)
+ vunmap(stream->data);
+}
new file mode 100644
@@ -0,0 +1,12 @@
+
+struct lu_stream {
+ mfn_t *pagelist;
+ size_t len;
+ int nr_pages;
+ char *data;
+};
+
+void *lu_stream_reserve(struct lu_stream *stream, size_t size);
+void lu_stream_end_reservation(struct lu_stream *stream, size_t size);
+int lu_stream_append(struct lu_stream *stream, void *data, size_t size);
+void lu_stream_free(struct lu_stream *stream);