xen: ask the hypervisor how much space it needs reserved

Ask the hypervisor how much space it needs reserved, since 32-on-64
doesn't need any space, and it may change in future.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 4186cb6a7f5a450160467005ecf7836b79b1b8cd..bc7bf5f8d077c33b1f269df8b2532345d309bf65 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1112,6 +1112,17 @@ static const struct machine_ops __initdata xen_machine_ops = {
 };
 
 
+static void __init xen_reserve_top(void)
+{
+       unsigned long top = HYPERVISOR_VIRT_START;
+       struct xen_platform_parameters pp;
+
+       if (HYPERVISOR_xen_version(XENVER_platform_parameters, &pp) == 0)
+               top = pp.virt_start;
+
+       reserve_top_address(-top + 2 * PAGE_SIZE);
+}
+
 /* First C function to be called on Xen boot */
 asmlinkage void __init xen_start_kernel(void)
 {
@@ -1169,7 +1180,7 @@ asmlinkage void __init xen_start_kernel(void)
                pv_info.kernel_rpl = 0;
 
        /* set the limit of our address space */
-       reserve_top_address(-HYPERVISOR_VIRT_START + 2 * PAGE_SIZE);
+       xen_reserve_top();
 
        /* set up basic CPUID stuff */
        cpu_detect(&new_cpu_data);