[Xen-devel] [PATCH 4/6] xen: add capability to load initrd outside of initial mapping

[Juergen Gross <jgross@xxxxxxxx>]

Modern pvops linux kernels support an initrd not covered by the initial
mapping. This capability is flagged by an elf-note.

In case the elf-note is set by the kernel don't place the initrd into
the initial mapping. This will allow to load larger initrds and/or
support domains with larger memory, as the initial mapping is limited
to 2GB and it is containing the p2m list.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 grub-core/loader/i386/xen.c        | 56 ++++++++++++++++++++++++++++++--------
 grub-core/loader/i386/xen_fileXX.c |  3 ++
 include/grub/xen_file.h            |  1 +
 3 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
index 65cec27..0f41048 100644
--- a/grub-core/loader/i386/xen.c
+++ b/grub-core/loader/i386/xen.c
@@ -307,15 +307,14 @@ grub_xen_pt_alloc (void)
 }
 
 static grub_err_t
-grub_xen_boot (void)
+grub_xen_alloc_end (void)
 {
   grub_err_t err;
-  grub_uint64_t nr_pages;
-  struct gnttab_set_version gnttab_setver;
-  grub_size_t i;
+  static int called = 0;
 
-  if (grub_xen_n_allocated_shared_pages)
-    return grub_error (GRUB_ERR_BUG, "active grants");
+  if (called)
+    return GRUB_ERR_NONE;
+  called = 1;
 
   err = grub_xen_p2m_alloc ();
   if (err)
@@ -327,6 +326,24 @@ grub_xen_boot (void)
   if (err)
     return err;
 
+  return GRUB_ERR_NONE;
+}
+
+static grub_err_t
+grub_xen_boot (void)
+{
+  grub_err_t err;
+  grub_uint64_t nr_pages;
+  struct gnttab_set_version gnttab_setver;
+  grub_size_t i;
+
+  if (grub_xen_n_allocated_shared_pages)
+    return grub_error (GRUB_ERR_BUG, "active grants");
+
+  err = grub_xen_alloc_end ();
+  if (err)
+    return err;
+
   err = set_mfns (console_pfn);
   if (err)
     return err;
@@ -587,6 +604,13 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ 
((unused)),
       goto fail;
     }
 
+  if (xen_inf.unmapped_initrd)
+    {
+      err = grub_xen_alloc_end ();
+      if (err)
+        goto fail;
+    }
+
   if (grub_initrd_init (argc, argv, &initrd_ctx))
     goto fail;
 
@@ -603,13 +627,22 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ 
((unused)),
        goto fail;
     }
 
-  next_start.mod_start = max_addr + xen_inf.virt_base;
-  next_start.mod_len = size;
-
-  max_addr = ALIGN_UP (max_addr + size, PAGE_SIZE);
+  if (xen_inf.unmapped_initrd)
+    {
+      next_start.flags |= SIF_MOD_START_PFN;
+      next_start.mod_start = max_addr >> PAGE_SHIFT;
+      next_start.mod_len = size;
+    }
+  else
+    {
+      next_start.mod_start = max_addr + xen_inf.virt_base;
+      next_start.mod_len = size;
+    }
 
   grub_dprintf ("xen", "Initrd, addr=0x%x, size=0x%x\n",
-               (unsigned) next_start.mod_start, (unsigned) size);
+               (unsigned) (max_addr + xen_inf.virt_base), (unsigned) size);
+
+  max_addr = ALIGN_UP (max_addr + size, PAGE_SIZE);
 
 fail:
   grub_initrd_close (&initrd_ctx);
@@ -660,6 +693,7 @@ grub_cmd_module (grub_command_t cmd __attribute__ 
((unused)),
 
   if (!xen_module_info_page)
     {
+      xen_inf.unmapped_initrd = 0;
       n_modules = 0;
       max_addr = ALIGN_UP (max_addr, PAGE_SIZE);
       modules_target_start = max_addr;
diff --git a/grub-core/loader/i386/xen_fileXX.c 
b/grub-core/loader/i386/xen_fileXX.c
index 1ba5649..69fccd2 100644
--- a/grub-core/loader/i386/xen_fileXX.c
+++ b/grub-core/loader/i386/xen_fileXX.c
@@ -253,6 +253,9 @@ 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 16:
+         xi->unmapped_initrd = !!grub_le_to_cpu32(*(grub_uint32_t *) desc);
+         break;
        default:
          grub_dprintf ("xen", "unknown note type %d\n", nh->n_type);
          break;
diff --git a/include/grub/xen_file.h b/include/grub/xen_file.h
index 4b2ccba..ed749fa 100644
--- a/include/grub/xen_file.h
+++ b/include/grub/xen_file.h
@@ -36,6 +36,7 @@ struct grub_xen_file_info
   int has_note;
   int has_xen_guest;
   int extended_cr3;
+  int unmapped_initrd;
   enum
   {
     GRUB_XEN_FILE_I386 = 1,
-- 
2.1.4


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