[Xen-changelog] x86/64 e820-parse-and-map code should skip low 1GB now as that

[Xen patchbot -3.0-testing <patchbot-3.0-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID fc7a39016601e9dd3161b91b294df1e9674ab383
# Parent  d3db967d299a9193972a1e466e9a090358d1ec26
x86/64 e820-parse-and-map code should skip low 1GB now as that
is mapped by the boot code.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r d3db967d299a -r fc7a39016601 xen/arch/x86/setup.c
--- a/xen/arch/x86/setup.c      Thu Apr 20 17:10:51 2006 +0100
+++ b/xen/arch/x86/setup.c      Thu Apr 20 17:11:12 2006 +0100
@@ -321,7 +321,7 @@ void __init __start_xen(multiboot_info_t
 #if defined (CONFIG_X86_64)
         /*
          * x86/64 maps all registered RAM. Points to note:
-         *  1. The initial pagetable already maps low 64MB, so skip that.
+         *  1. The initial pagetable already maps low 1GB, so skip that.
          *  2. We must map *only* RAM areas, taking care to avoid I/O holes.
          *     Failure to do this can cause coherency problems and deadlocks
          *     due to cache-attribute mismatches (e.g., AMD/AGP Linux bug).
@@ -329,13 +329,14 @@ void __init __start_xen(multiboot_info_t
         {
             /* Calculate page-frame range, discarding partial frames. */
             unsigned long start, end;
+            unsigned long init_mapped = 1UL << (30 - PAGE_SHIFT); /* 1GB */
             start = PFN_UP(e820.map[i].addr);
             end   = PFN_DOWN(e820.map[i].addr + e820.map[i].size);
             /* Clip the range to above 64MB. */
-            if ( end < (64UL << (20-PAGE_SHIFT)) )
+            if ( end < init_mapped )
                 continue;
-            if ( start < (64UL << (20-PAGE_SHIFT)) )
-                start = 64UL << (20-PAGE_SHIFT);
+            if ( start < init_mapped )
+                start = init_mapped;
             /* Request the mapping. */
             map_pages_to_xen(
                 PAGE_OFFSET + (start << PAGE_SHIFT),

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