libxc: Domain builder must align initial virtual mapping to 4MB

boundaries.
From: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Keir Fraser <keir@xensource.com>

tools/libxc/xc_dom_core.c

@@ -717,6 +717,9 @@ int xc_dom_build_image(struct xc_dom_image *dom)
     }
     page_size = XC_DOM_PAGE_SIZE(dom);
 
+    /* 4MB align virtual base address */
+    dom->parms.virt_base &= ~(((uint64_t)1<<22)-1);
+
     /* load kernel */
     if (0 != xc_dom_alloc_segment(dom, &dom->kernel_seg, "kernel",
 				  dom->kernel_seg.vstart,

tools/libxc/xc_dom_x86.c

@@ -66,11 +66,12 @@ static int count_pgtables(struct xc_dom_image *dom, int pae,
 
     extra_pages = dom->alloc_bootstack ? 1 : 0;
     extra_pages += dom->extra_pages;
+    extra_pages += 128; /* 512kB padding */
     pages = extra_pages;
     for (;;)
     {
 	try_virt_end = round_up(dom->virt_alloc_end + pages * PAGE_SIZE_X86,
-				bits_to_mask(l1_bits));
+				bits_to_mask(22)); /* 4MB alignment */
 	dom->pg_l4 =
 	    nr_page_tables(dom->parms.virt_base, try_virt_end, l4_bits);
 	dom->pg_l3 =
@@ -313,6 +314,7 @@ static int alloc_magic_pages(struct xc_dom_image *dom)
     if (xc_dom_feature_translated(dom))
 	dom->shared_info_pfn = xc_dom_alloc_page(dom, "shared info");
     dom->alloc_bootstack = 1;
+
     return 0;
 }