xen: add capability to load p2m list outside of kernel mapping

Modern pvops linux kernels support a p2m list not covered by the
kernel mapping. This capability is flagged by an elf-note specifying
the virtual address the kernel is expecting the p2m list to be mapped
to.

In case the elf-note is set by the kernel don't place the p2m list
into the kernel mapping, but map it to the given address. This will
allow to support domains with larger memory, as the kernel mapping is
limited to 2GB and a domain with huge memory in the TB range will have
a p2m list larger than this.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/loader/i386/xen.c

@@ -313,24 +313,50 @@ static grub_err_t
 grub_xen_p2m_alloc (void)
 {
   grub_relocator_chunk_t ch;
-  grub_size_t p2msize;
+  grub_size_t p2msize, p2malloc;
   grub_err_t err;
+  struct grub_xen_mapping *map;
 
   if (xen_state.virt_mfn_list)
     return GRUB_ERR_NONE;
 
+  map = xen_state.mappings + xen_state.n_mappings;
+  p2msize = ALIGN_UP (sizeof (grub_xen_mfn_t) *
+		      grub_xen_start_page_addr->nr_pages, PAGE_SIZE);
+  if (xen_state.xen_inf.has_p2m_base)
+    {
+      err = get_pgtable_size (xen_state.xen_inf.p2m_base,
+			      xen_state.xen_inf.p2m_base + p2msize,
+			      (xen_state.max_addr + p2msize) >> PAGE_SHIFT);
+      if (err)
+	return err;
+
+      map->area.pfn_start = xen_state.max_addr >> PAGE_SHIFT;
+      p2malloc = p2msize + page2offset (map->area.n_pt_pages);
+      xen_state.n_mappings++;
+      xen_state.next_start.mfn_list = xen_state.xen_inf.p2m_base;
+      xen_state.next_start.first_p2m_pfn = map->area.pfn_start;
+      xen_state.next_start.nr_p2m_frames = p2malloc >> PAGE_SHIFT;
+    }
+  else
+    {
+      xen_state.next_start.mfn_list =
+	xen_state.max_addr + xen_state.xen_inf.virt_base;
+      p2malloc = p2msize;
+    }
+
   xen_state.state.mfn_list = xen_state.max_addr;
-  xen_state.next_start.mfn_list =
-    xen_state.max_addr + xen_state.xen_inf.virt_base;
-  p2msize = sizeof (grub_xen_mfn_t) * grub_xen_start_page_addr->nr_pages;
   err = grub_relocator_alloc_chunk_addr (xen_state.relocator, &ch,
-					 xen_state.max_addr, p2msize);
+					 xen_state.max_addr, p2malloc);
   if (err)
     return err;
   xen_state.virt_mfn_list = get_virtual_current_address (ch);
+  if (xen_state.xen_inf.has_p2m_base)
+    map->where = (grub_uint64_t *) xen_state.virt_mfn_list +
+		 p2msize / sizeof (grub_uint64_t);
   grub_memcpy (xen_state.virt_mfn_list,
 	       (void *) grub_xen_start_page_addr->mfn_list, p2msize);
-  xen_state.max_addr = ALIGN_UP (xen_state.max_addr + p2msize, PAGE_SIZE);
+  xen_state.max_addr += p2malloc;
 
   return GRUB_ERR_NONE;
 }
@@ -448,9 +474,12 @@ grub_xen_alloc_boot_data (void)
 {
   grub_err_t err;
 
-  err = grub_xen_p2m_alloc ();
+  if (!xen_state.xen_inf.has_p2m_base)
-  if (err)
+    {
-    return err;
+      err = grub_xen_p2m_alloc ();
+      if (err)
+	return err;
+    }
   err = grub_xen_special_alloc ();
   if (err)
     return err;
@@ -475,6 +504,12 @@ grub_xen_boot (void)
   err = grub_xen_alloc_boot_data ();
   if (err)
     return err;
+  if (xen_state.xen_inf.has_p2m_base)
+    {
+      err = grub_xen_p2m_alloc ();
+      if (err)
+	return err;
+    }
 
   err = set_mfns (xen_state.console_pfn);
   if (err)

grub-core/loader/i386/xen_fileXX.c

@@ -261,6 +261,10 @@ parse_note (grub_elf_t elf, struct grub_xen_file_info *xi,
 					  descsz == 2 ? 2 : 3) == 0)
 	    xi->arch = GRUB_XEN_FILE_I386;
 	  break;
+	case XEN_ELFNOTE_INIT_P2M:
+	  xi->p2m_base = grub_le_to_cpu_addr (*(Elf_Addr *) desc);
+	  xi->has_p2m_base = 1;
+	  break;
 	case XEN_ELFNOTE_MOD_START_PFN:
 	  xi->unmapped_initrd = !!grub_le_to_cpu32(*(grub_uint32_t *) desc);
 	  break;

include/grub/xen_file.h

@@ -32,9 +32,11 @@ struct grub_xen_file_info
   grub_uint64_t entry_point;
   grub_uint64_t hypercall_page;
   grub_uint64_t paddr_offset;
+  grub_uint64_t p2m_base;
   int has_hypercall_page;
   int has_note;
   int has_xen_guest;
+  int has_p2m_base;
   int extended_cr3;
   int unmapped_initrd;
   enum