xen/i386: follow-up to "replace order-based range checking of M2P table by linear...

The numbers obtained from the hypervisor really can't ever lead to an
overflow here, only the original calculation going through the order
of the range could have. This avoids the (as Jeremy points outs)
somewhat ugly NULL-based calculation here.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5f76c0acb2c7116e6884f27743884e6b9497c52c..e805b6dd7c659a245bea4d00d5e93b119fed566c 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1634,10 +1634,8 @@ void __init xen_setup_machphys_mapping(void)
                machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
        }
 #ifdef CONFIG_X86_32
-       if ((machine_to_phys_mapping + machine_to_phys_nr)
-           < machine_to_phys_mapping)
-               machine_to_phys_nr = (unsigned long *)NULL
-                                    - machine_to_phys_mapping;
+       WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
+               < machine_to_phys_mapping);
 #endif
 }