[Xen-devel] [PATCH] limit Xen heap size to 2Gb

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

.. in order to avoid stub code created on the stack being unable to
reach targets in main Xen code via direct branches.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: 2006-09-11/xen/arch/x86/setup.c
===================================================================
--- 2006-09-11.orig/xen/arch/x86/setup.c        2006-09-18 16:11:12.000000000 
+0200
+++ 2006-09-11/xen/arch/x86/setup.c     2006-09-19 08:51:29.000000000 +0200
@@ -273,6 +273,13 @@ void __init __start_xen(multiboot_info_t
         EARLY_FAIL();
     }
 
+    /*
+     * Since there are some stubs getting built on the stacks which use
+     * direct calls/jumps, the heap must be confined to the lower 2G so
+     * that those branches can reach their targets.
+     */
+    if ( opt_xenheap_megabytes > 2048 )
+        opt_xenheap_megabytes = 2048;
     xenheap_phys_end = opt_xenheap_megabytes << 20;
 
     if ( mbi->flags & MBI_MEMMAP )


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