[Xen-devel] [PATCH v6 11/15] x86: change default load address from 1 MiB to 2 MiB

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

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 <daniel.kiper@xxxxxxxxxx>
---
 xen/arch/x86/Makefile  |    2 +-
 xen/arch/x86/Rules.mk  |    4 ++++
 xen/arch/x86/setup.c   |    3 ++-
 xen/arch/x86/xen.lds.S |    2 +-
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index d8fe0f1..6dae654 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) -nr $(TARGET)-syms | awk '$$3 == "_end" {print "0x"$$1}'`
 
 .PHONY: tests
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index 42be4bc..dd10afe 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -1,6 +1,10 @@
 ########################################
 # x86-specific definitions
 
+XEN_IMG_OFFSET = 0x200000
+
+CFLAGS += -DXEN_IMG_OFFSET=$(XEN_IMG_OFFSET)
+
 CFLAGS += -I$(BASEDIR)/include
 CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-generic
 CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-default
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 d7bd03e..8bfbd97 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 */
-- 
1.7.10.4


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