[Xen-devel] [PATCH v8 09/13] 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... :-)))

Additionally, drop first 2 MiB mapping from Xen image mapping.
It is no longer needed.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
---
v8 - suggestions/fixes:
   - drop first 2 MiB mapping from Xen image mapping
     (suggested by Jan Beulich),
   - improve commit message.

v7 - suggestions/fixes:
   - minor cleanups
     (suggested by Jan Beulich).
---
 xen/arch/x86/Makefile      |    2 +-
 xen/arch/x86/Rules.mk      |    3 +++
 xen/arch/x86/boot/head.S   |    8 --------
 xen/arch/x86/boot/x86_64.S |    5 +++--
 xen/arch/x86/setup.c       |    3 ++-
 xen/arch/x86/xen.lds.S     |    2 +-
 6 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 8b68c06..b3c4a40 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$$/0x\1/p'`
 
 ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o 
$(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
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/boot/head.S b/xen/arch/x86/boot/head.S
index bda7248..1de4f1a 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -479,14 +479,6 @@ trampoline_setup:
         mov     %eax,sym_phys(boot_tsc_stamp)
         mov     %edx,sym_phys(boot_tsc_stamp+4)
 
-        /*
-         * During boot, hook 4kB mappings of first 2MB of memory into L2.
-         * This avoids mixing cachability for the legacy VGA region, and is
-         * corrected when Xen relocates itself.
-         */
-        mov     $sym_phys(l1_identmap)+__PAGE_HYPERVISOR,%edi
-        mov     %edi,sym_phys(l2_xenmap)
-
         /* Apply relocations to bootstrap trampoline. */
         mov     sym_phys(trampoline_phys),%edx
         mov     $sym_phys(__trampoline_rel_start),%edi
diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
index 139b2ca..7890374 100644
--- a/xen/arch/x86/boot/x86_64.S
+++ b/xen/arch/x86/boot/x86_64.S
@@ -121,8 +121,9 @@ GLOBAL(l2_identmap)
  * page.
  */
 GLOBAL(l2_xenmap)
-        idx = 0
-        .rept 8
+        .quad 0
+        idx = 1
+        .rept 7
         .quad sym_phys(__image_base__) + (idx << L2_PAGETABLE_SHIFT) + 
(PAGE_HYPERVISOR | _PAGE_PSE)
         idx = idx + 1
         .endr
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 e0e2529..45251fd 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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