libxc: create unmapped initrd in domain builder if supported

In case the kernel of a new pv-domU indicates it is supporting an
unmapped initrd, don't waste precious virtual space for the initrd,
but allocate only guest physical memory for it.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxc/include/xc_dom.h

@@ -97,6 +97,11 @@ struct xc_dom_image {
     xen_pfn_t pfn_alloc_end;
     xen_vaddr_t virt_alloc_end;
     xen_vaddr_t bsd_symtab_start;
+
+    /* initrd parameters as specified in start_info page */
+    unsigned long initrd_start;
+    unsigned long initrd_len;
+
     unsigned int alloc_bootstack;
     xen_vaddr_t virt_pgtab_end;
 

tools/libxc/xc_dom_core.c

@@ -1041,6 +1041,7 @@ static int xc_dom_build_ramdisk(struct xc_dom_image *dom)
 int xc_dom_build_image(struct xc_dom_image *dom)
 {
     unsigned int page_size;
+    bool unmapped_initrd;
 
     DOMPRINTF_CALLED(dom->xch);
 
@@ -1064,11 +1065,15 @@ int xc_dom_build_image(struct xc_dom_image *dom)
     if ( dom->kernel_loader->loader(dom) != 0 )
         goto err;
 
-    /* load ramdisk */
-    if ( dom->ramdisk_blob )
+    /* Don't load ramdisk now if no initial mapping required. */
+    unmapped_initrd = dom->parms.unmapped_initrd && !dom->ramdisk_seg.vstart;
+
+    if ( dom->ramdisk_blob && !unmapped_initrd )
     {
         if ( xc_dom_build_ramdisk(dom) != 0 )
             goto err;
+        dom->initrd_start = dom->ramdisk_seg.vstart;
+        dom->initrd_len = dom->ramdisk_seg.vend - dom->ramdisk_seg.vstart;
     }
 
     /* load devicetree */
@@ -1106,6 +1111,16 @@ int xc_dom_build_image(struct xc_dom_image *dom)
     if ( dom->virt_pgtab_end && xc_dom_alloc_pad(dom, dom->virt_pgtab_end) )
         return -1;
 
+    /* Load ramdisk if no initial mapping required. */
+    if ( dom->ramdisk_blob && unmapped_initrd )
+    {
+        if ( xc_dom_build_ramdisk(dom) != 0 )
+            goto err;
+        dom->flags |= SIF_MOD_START_PFN;
+        dom->initrd_start = dom->ramdisk_seg.pfn;
+        dom->initrd_len = page_size * dom->ramdisk_seg.pages;
+    }
+
     return 0;
 
  err:

tools/libxc/xc_dom_x86.c

@@ -663,8 +663,8 @@ static int start_info_x86_32(struct xc_dom_image *dom)
 
     if ( dom->ramdisk_blob )
     {
-        start_info->mod_start = dom->ramdisk_seg.vstart;
-        start_info->mod_len = dom->ramdisk_seg.vend - dom->ramdisk_seg.vstart;
+        start_info->mod_start = dom->initrd_start;
+        start_info->mod_len = dom->initrd_len;
     }
 
     if ( dom->cmdline )
@@ -710,8 +710,8 @@ static int start_info_x86_64(struct xc_dom_image *dom)
 
     if ( dom->ramdisk_blob )
     {
-        start_info->mod_start = dom->ramdisk_seg.vstart;
-        start_info->mod_len = dom->ramdisk_seg.vend - dom->ramdisk_seg.vstart;
+        start_info->mod_start = dom->initrd_start;
+        start_info->mod_len = dom->initrd_len;
     }
 
     if ( dom->cmdline )