xen/x86: Do not call xen_init_time_ops() until shared_info is initialized

Routines that are set by xen_init_time_ops() use shared_info's
pvclock_vcpu_time_info area. This area is not properly available until
shared_info is mapped in xen_setup_shared_info().

This became especially problematic due to commit dd759d93f4dd ("x86/timers:
Add simple udelay calibration") where we end up reading tsc_to_system_mul
from xen_dummy_shared_info (i.e. getting zero value) and then trying
to divide by it in pvclock_tsc_khz().

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
OraBug: 26662731

(cherry picked from commit d162809f85b4f54ef075517ffa2f3d02e55d5a53)
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Conflicts:
	arch/x86/xen/enlighten_pv.c
	(No enlighten_pv.c in our tree. Note also that
         we don't have dd759d93f4dd. Still, this fixes a
         latent bug).

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 42c6fefbbe19c6c09334aad021df8dc622115a94..96062f109fbb413bd4389181290e69d3eea80c55 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1160,6 +1160,13 @@ void xen_setup_shared_info(void)
 #endif
 
        xen_setup_mfn_list_list();
+
+       /*
+        * Now that shared info is set up we can start using routines that
+        * point to pvclock area.
+        */
+       if (system_state == SYSTEM_BOOTING)
+               xen_init_time_ops();
 }
 
 /* This is called once we have the cpu_possible_mask */
@@ -1505,8 +1512,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
        x86_init.oem.arch_setup = xen_arch_setup;
        x86_init.oem.banner = xen_banner;
 
-       xen_init_time_ops();
-
        /*
         * Set up some pagetable state before starting to set any ptes.
         */

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index a4f0e5d89c4f0636cb4f3e43524af60af7a32023..66e320c00db549baf36acc68200ba2a5693e0846 100644 (file)
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -504,7 +504,7 @@ static void __init xen_time_init(void)
                pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
 }
 
-void __init xen_init_time_ops(void)
+void __ref xen_init_time_ops(void)
 {
        pv_time_ops = xen_time_ops;