[PATCH] powerpc: Auto reserve of device tree blob

A devtree compiler (dtc) generated devtree blob is "relocatable" and so
does not contain a reserved_map entry for the blob itself.  This means
that if passed to Linux, Linux will not get lmb_reserve() the blob and
it could be over.  The following patch will explicitly reserve the
"blob" as it was given to us and stops prom_init.c from creating a
reserved mapping for the blob.

NOTE: that the dtc/kexec should not generate the blob reservation entry.
Although if they do, LMB reserver handles overlaps.

Signed-off-by:  <jimix@watson.ibm.com>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 9 insertions, 5 deletions

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 8d0415b080bb..969f4abcc0be 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1267,6 +1267,11 @@ static void __init early_reserve_mem(void)
 
         reserve_map = (u64 *)(((unsigned long)initial_boot_params) +
                                         initial_boot_params->off_mem_rsvmap);
+
+        /* before we do anything, lets reserve the dt blob */
+        lmb_reserve(__pa((unsigned long)initial_boot_params),
+                    initial_boot_params->totalsize);
+
 #ifdef CONFIG_PPC32
         /* 
          * Handle the case where we might be booting from an old kexec
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 2442361772e2..98e201c38d27 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -1950,11 +1950,7 @@ static void __init flatten_device_tree(void)
         /* Version 16 is not backward compatible */
         hdr->last_comp_version = 0x10;
 
-        /* Reserve the whole thing and copy the reserve map in, we
-         * also bump mem_reserve_cnt to cause further reservations to
-         * fail since it's too late.
-         */
-        reserve_mem(RELOC(dt_header_start), hdr->totalsize);
+        /* Copy the reserve map in */
         memcpy(rsvmap, RELOC(mem_reserve_map), sizeof(mem_reserve_map));
 
 #ifdef DEBUG_PROM
@@ -1967,6 +1963,9 @@ static void __init flatten_device_tree(void)
                                     RELOC(mem_reserve_map)[i].size);
         }
 #endif
+        /* Bump mem_reserve_cnt to cause further reservations to fail
+         * since it's too late.
+         */
         RELOC(mem_reserve_cnt) = MEM_RESERVE_MAP_SIZE;
 
         prom_printf("Device tree strings 0x%x -> 0x%x\n",