libxc: set flag for support of linear p2m list in domain builder

Set the SIF_VIRT_P2M_4TOOLS flag for pv-domUs in the domain builder
to indicate the Xen tools have full support for the virtual mapped
linear p2m list.

This will enable pv-domUs to drop support of the 3 level p2m tree
and use the linear list only. Without setting this flag some kernels
might limit themselves to 512 GB memory size in order not to break
migration.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

docs/features/migration.pandoc

@@ -1,5 +1,5 @@
 % Migration
-% Revision 1
+% Revision 2
 
 \clearpage
 
@@ -95,7 +95,6 @@ scenarios, which will involve starting with VMs from Xen 4.5
 # Areas for improvement
 
 * Arm support
-* Linear P2M support for x86 PV
 * Live looping parameters
 
 # Known issues
@@ -105,7 +104,8 @@ scenarios, which will involve starting with VMs from Xen 4.5
 * x86 HVM with nested-virt (no relevant information included in the
   stream)
 * x86 PV ballooning (P2M marked dirty, target frame not marked)
-* x86 PV P2M structure changes (not noticed, stale mappings used)
+* x86 PV P2M structure changes (not noticed, stale mappings used) for
+  guests not using the linear p2m layout
 
 # References
 
@@ -120,4 +120,5 @@ for Migration v2
 Date       Revision Version  Notes
 ---------- -------- -------- -------------------------------------------
 2015-10-24 1        Xen 4.6  Document written
+2015-12-11 2        Xen 4.7  Support of linear p2m list
 ---------- -------- -------- -------------------------------------------

tools/libxc/xc_dom_compat_linux.c

@@ -59,7 +59,7 @@ int xc_linux_build(xc_interface *xch, uint32_t domid,
          ((rc = xc_dom_ramdisk_file(dom, initrd_name)) != 0) )
         goto out;
 
-    dom->flags = flags;
+    dom->flags |= flags;
     dom->console_evtchn = console_evtchn;
     dom->xenstore_evtchn = store_evtchn;
 

tools/libxc/xc_dom_core.c

@@ -777,6 +777,8 @@ struct xc_dom_image *xc_dom_allocate(xc_interface *xch,
     dom->parms.elf_paddr_offset = UNSET_ADDR;
     dom->parms.p2m_base = UNSET_ADDR;
 
+    dom->flags = SIF_VIRT_P2M_4TOOLS;
+
     dom->alloc_malloc += sizeof(*dom);
     return dom;