[Xen-devel] [PATCH 6/6] xen: add capability to load p2m list outside of kernel mapping

[Juergen Gross <jgross@xxxxxxxx>]

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@xxxxxxxx>
---
 grub-core/loader/i386/xen.c        | 50 ++++++++++++++++++++++++++++++++------
 grub-core/loader/i386/xen_fileXX.c |  4 +++
 include/grub/xen_file.h            |  2 ++
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
index 5e10420..9ddc6c2 100644
--- a/grub-core/loader/i386/xen.c
+++ b/grub-core/loader/i386/xen.c
@@ -305,19 +305,44 @@ 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;
+
+  map = mappings + n_mappings;
+  p2msize = ALIGN_UP (sizeof (grub_xen_mfn_t) *
+                     grub_xen_start_page_addr->nr_pages, PAGE_SIZE);
+  if (xen_inf.has_p2m_base)
+    {
+      err = get_pgtable_size (xen_inf.p2m_base, xen_inf.p2m_base + p2msize,
+                             (max_addr + p2msize) >> PAGE_SHIFT);
+      if (err)
+       return err;
+
+      map->area.pfn_start = max_addr >> PAGE_SHIFT;
+      p2malloc = p2msize + page2offset (map->area.n_pt_pages);
+      n_mappings++;
+      next_start.mfn_list = xen_inf.p2m_base;
+      next_start.first_p2m_pfn = map->area.pfn_start;
+      next_start.nr_p2m_frames = p2malloc >> PAGE_SHIFT;
+    }
+  else
+    {
+      next_start.mfn_list = max_addr + xen_inf.virt_base;
+      p2malloc = p2msize;
+    }
 
   state.mfn_list = max_addr;
-  next_start.mfn_list = max_addr + xen_inf.virt_base;
-  p2msize = sizeof (grub_xen_mfn_t) * grub_xen_start_page_addr->nr_pages;
-  err = grub_relocator_alloc_chunk_addr (relocator, &ch, max_addr, p2msize);
+  err = grub_relocator_alloc_chunk_addr (relocator, &ch, max_addr, p2malloc);
   if (err)
     return err;
   virt_mfn_list = get_virtual_current_address (ch);
+  if (xen_inf.has_p2m_base)
+    map->where = (grub_uint64_t *) virt_mfn_list +
+                p2msize / sizeof (grub_uint64_t);
   grub_memcpy (virt_mfn_list,
               (void *) grub_xen_start_page_addr->mfn_list, p2msize);
-  max_addr = ALIGN_UP (max_addr + p2msize, PAGE_SIZE);
+  max_addr += p2malloc;
 
   return GRUB_ERR_NONE;
 }
@@ -425,9 +450,12 @@ grub_xen_alloc_end (void)
     return GRUB_ERR_NONE;
   called = 1;
 
-  err = grub_xen_p2m_alloc ();
-  if (err)
-    return err;
+  if (!xen_inf.has_p2m_base)
+    {
+      err = grub_xen_p2m_alloc ();
+      if (err)
+       return err;
+    }
   err = grub_xen_special_alloc ();
   if (err)
     return err;
@@ -452,6 +480,12 @@ grub_xen_boot (void)
   err = grub_xen_alloc_end ();
   if (err)
     return err;
+  if (xen_inf.has_p2m_base)
+    {
+      err = grub_xen_p2m_alloc ();
+      if (err)
+       return err;
+    }
 
   err = set_mfns (console_pfn);
   if (err)
diff --git a/grub-core/loader/i386/xen_fileXX.c 
b/grub-core/loader/i386/xen_fileXX.c
index 69fccd2..8d01adb 100644
--- a/grub-core/loader/i386/xen_fileXX.c
+++ b/grub-core/loader/i386/xen_fileXX.c
@@ -253,6 +253,10 @@ 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 15:
+         xi->p2m_base = grub_le_to_cpu_addr (*(Elf_Addr *) desc);
+         xi->has_p2m_base = 1;
+         break;
        case 16:
          xi->unmapped_initrd = !!grub_le_to_cpu32(*(grub_uint32_t *) desc);
          break;
diff --git a/include/grub/xen_file.h b/include/grub/xen_file.h
index ed749fa..6587999 100644
--- a/include/grub/xen_file.h
+++ b/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
-- 
2.1.4


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