[PATCH] x86: keep the crash kernel below 896 MiB

[Warner Wang <warner.wang@hp.com>]

When use the crashkernel=size parameter without specifying a "@xM"
suffix, the crashkernel will be reserved at the highest suitable
address of memory, this will make the kexec-tools fail to work.
The current kexec-tools have a limitation that it can only work
with crashkernel reserved under 896 MiB.  we can increase this
limit once kexec-tools are fixed.
Linux kernel itself have this code for kexec-tools limitation,
so I think Xen code should also have it.

Signed-off-by: Warner Wang <warner.wang@hp.com>
---
 xen/arch/x86/setup.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 43301a5..ae4c947 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -943,6 +943,13 @@ void __init __start_xen(unsigned long mbi_p)
             }
         }
 
+        /*
+         * Keep the crash kernel below this limit.  On 64 bits, kexec-tools
+         * currently limits us to 896 MiB; increase this limit once kexec-tools
+         * are fixed.
+         */
+        e = min_t(uint64_t, e, 896 << 20);
+
         /* Don't overlap with modules. */
         e = consider_modules(s, e, PAGE_ALIGN(kexec_crash_area.size),
                              mod, mbi->mods_count, -1);
-- 
1.7.1