1 files changed, 12 insertions, 0 deletions

diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c
index 031dc1dcf819..42756771b8eb 100644
--- a/arch/i386/xen/enlighten.c
+++ b/arch/i386/xen/enlighten.c
@@ -291,6 +291,18 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
         load_TLS_descriptor(t, cpu, 2);
 
         xen_mc_issue(PARAVIRT_LAZY_CPU);
+
+        /*
+         * XXX sleazy hack: If we're being called in a lazy-cpu zone,
+         * it means we're in a context switch, and %gs has just been
+         * saved.  This means we can zero it out to prevent faults on
+         * exit from the hypervisor if the next process has no %gs.
+         * Either way, it has been saved, and the new value will get
+         * loaded properly.  This will go away as soon as Xen has been
+         * modified to not save/restore %gs for normal hypercalls.
+         */
+        if (xen_get_lazy_mode() == PARAVIRT_LAZY_CPU)
+                loadsegment(gs, 0);
 }
 
 static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,