[v7,10/14] x86: change default load address from 1 MiB to 2 MiB

Commit Message

Daniel Kiper Sept. 23, 2016, 9:47 p.m. UTC

Subsequent patches introducing relocatable early boot code play with
page tables using 2 MiB huge pages. If load address is not aligned at
2 MiB then code touching such page tables must have special cases for
start and end of Xen image memory region. So, let's make life easier
and move default load address from 1 MiB to 2 MiB. This way page table
code will be nice and easy. Hence, there is a chance that it will be
less error prone too... :-)))

Signed-off-by: Daniel Kiper <[e-mail]>
Acked-by: Jan Beulich <[e-mail]>
---
v7 - suggestions/fixes:
   - minor cleanups
     (suggested by Jan Beulich).
---
 xen/arch/x86/Makefile  |    2 +-
 xen/arch/x86/Rules.mk  |    3 +++
 xen/arch/x86/setup.c   |    3 ++-
 xen/arch/x86/xen.lds.S |    2 +-
 4 files changed, 7 insertions(+), 3 deletions(-)

Patch

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 7d37728..04cc59f 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -90,7 +90,7 @@  all_symbols =
 endif
 
 $(TARGET): $(TARGET)-syms $(efi-y) boot/mkelf32
-	./boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(TARGET) 0x100000 \
+	./boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(TARGET) $(XEN_IMG_OFFSET) \
 		`$(NM) $(TARGET)-syms | sed -ne 's/^\([^ ]*\) . __end_of_image__$$/0x\1/p'`
 
 .PHONY: tests
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index 42be4bc..36e6386 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -1,9 +1,12 @@ 
 ########################################
 # x86-specific definitions
 
+XEN_IMG_OFFSET := 0x200000
+
 CFLAGS += -I$(BASEDIR)/include
 CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-generic
 CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-default
+CFLAGS += -DXEN_IMG_OFFSET=$(XEN_IMG_OFFSET)
 CFLAGS += '-D__OBJECT_LABEL__=$(subst /,$$,$(subst -,_,$(subst $(BASEDIR)/,,$(CURDIR))/$@))'
 
 # Prevent floating-point variables from creeping into Xen.
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 5b17783..f19af6e 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -957,7 +957,8 @@  void __init noreturn __start_xen(unsigned long mbi_p)
              * Undo the temporary-hooking of the l1_identmap.  __2M_text_start
              * is contained in this PTE.
              */
-            BUG_ON(l2_table_offset((unsigned long)_erodata) ==
+            BUG_ON(using_2M_mapping() &&
+                   l2_table_offset((unsigned long)_erodata) ==
                    l2_table_offset((unsigned long)_stext));
             *pl2e++ = l2e_from_pfn(xen_phys_start >> PAGE_SHIFT,
                                    PAGE_HYPERVISOR_RX | _PAGE_PSE);
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index f4b4e99..d9561e5 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -55,7 +55,7 @@  SECTIONS
   __2M_text_start = .;         /* Start of 2M superpages, mapped RX. */
 #endif
 
-  . = __XEN_VIRT_START + MB(1);
+  . = __XEN_VIRT_START + XEN_IMG_OFFSET;
   _start = .;
   .text : {
         _stext = .;            /* Text and read-only data */