From: Rik van Riel <riel@redhat.com>
Date: Wed, 13 Aug 2008 15:49:24 -0400
Subject: [xen] automatically make heap larger on large mem system
Message-id: 20080813154924.6c291dba@cuia.bos.redhat.com
O-Subject: [PATCH RHEL 5.3][1/2] automatically make xen heap larger on large memory systems
Bugzilla: 453467
RH-Acked-by: Chris Lalancette <clalance@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>
RH-Acked-by: Bill Burns <bburns@redhat.com>

On very large memory systems the allocation bitmap does not fit in the
Xen heap, causing the system to crash very early on during boot.  The
workaround is to specify xenheap_megabytes=number at boot time.

This patch makes the larger allocation bitmap automatic on very large
memory systems.

Together with patch 2/2, fixes bug 453467.

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1216730216 -3600
# Node ID a637c023e066e972d03e95b1359786e72f32d2be
# Parent  fc44e35b39136449247d3f9d013776f8fe3ba9db
x86/64: Account for allocation bitmap by making Xen heap appropriately larger.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/arch/x86/setup.c b/arch/x86/setup.c
index f3c7b8a..fdb1d1d 100644
--- a/arch/x86/setup.c
+++ b/arch/x86/setup.c
@@ -547,14 +547,6 @@ void __init __start_xen(unsigned long mbi_p)
     if ( ((unsigned long)cpu0_stack & (STACK_SIZE-1)) != 0 )
         EARLY_FAIL("Misaligned CPU0 stack.\n");
 
-    /*
-     * 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;
-
     if ( e820_raw_nr != 0 )
     {
         memmap_type = "Xen-e820";
@@ -627,6 +619,23 @@ void __init __start_xen(unsigned long mbi_p)
     /* Sanitise the raw E820 map to produce a final clean version. */
     max_page = init_e820(memmap_type, e820_raw, &e820_raw_nr);
 
+#ifdef CONFIG_X86_64
+    /*
+     * On x86/64 we are able to account for the allocation bitmap
+     * (allocated in common/page_alloc.c:init_boot_allocator()) stealing
+     * from the Xen heap. Here we make the Xen heap appropriately larger.
+     */
+    opt_xenheap_megabytes += (max_page / 8) >> 20;
+#endif
+
+    /*
+     * 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;
+
     /* Create a temporary copy of the E820 map. */
     memcpy(&boot_e820, &e820, sizeof(e820));