Upgrade to 4.4.50-rt62

[kvmfornfv.git] / kernel / arch / x86 / kernel / process_64.c

diff --git a/kernel/arch/x86/kernel/process_64.c b/kernel/arch/x86/kernel/process_64.c
index e835d26..4cbb60f 100644 (file)
--- a/kernel/arch/x86/kernel/process_64.c
+++ b/kernel/arch/x86/kernel/process_64.c
@@ -48,6 +48,7 @@
 #include <asm/syscalls.h>
 #include <asm/debugreg.h>
 #include <asm/switch_to.h>
+#include <asm/xen/hypervisor.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -411,6 +412,17 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
                     task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
                __switch_to_xtra(prev_p, next_p, tss);
 
+#ifdef CONFIG_XEN
+       /*
+        * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
+        * current_pt_regs()->flags may not match the current task's
+        * intended IOPL.  We need to switch it manually.
+        */
+       if (unlikely(static_cpu_has(X86_FEATURE_XENPV) &&
+                    prev->iopl != next->iopl))
+               xen_set_iopl_mask(next->iopl);
+#endif
+
        if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
                /*
                 * AMD CPUs have a misfeature: SYSRET sets the SS selector but