x86/paravirt: flush pending mmu updates on context switch

Impact: allow preemption during lazy mmu updates

If we're in lazy mmu mode when context switching, leave
lazy mmu mode, but remember the task's state in
TIF_LAZY_MMU_UPDATES.  When we resume the task, check this
flag and re-enter lazy mmu mode if its set.

This sets things up for allowing lazy mmu mode while preemptible,
though that won't actually be active until the next change.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
index 2cc4a90e2cb3..950929c607d3 100644
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -473,16 +473,22 @@ static void vmi_enter_lazy_cpu(void)
         vmi_ops.set_lazy_mode(2);
 }
 
+static void vmi_leave_lazy_cpu(void)
+{
+        vmi_ops.set_lazy_mode(0);
+        paravirt_leave_lazy_cpu();
+}
+
 static void vmi_enter_lazy_mmu(void)
 {
         paravirt_enter_lazy_mmu();
         vmi_ops.set_lazy_mode(1);
 }
 
-static void vmi_leave_lazy(void)
+static void vmi_leave_lazy_mmu(void)
 {
-        paravirt_leave_lazy(paravirt_get_lazy_mode());
         vmi_ops.set_lazy_mode(0);
+        paravirt_leave_lazy_mmu();
 }
 
 static inline int __init check_vmi_rom(struct vrom_header *rom)
@@ -718,12 +724,12 @@ static inline int __init activate_vmi(void)
 
         para_wrap(pv_cpu_ops.lazy_mode.enter, vmi_enter_lazy_cpu,
                   set_lazy_mode, SetLazyMode);
-        para_wrap(pv_cpu_ops.lazy_mode.leave, vmi_leave_lazy,
+        para_wrap(pv_cpu_ops.lazy_mode.leave, vmi_leave_lazy_cpu,
                   set_lazy_mode, SetLazyMode);
 
         para_wrap(pv_mmu_ops.lazy_mode.enter, vmi_enter_lazy_mmu,
                   set_lazy_mode, SetLazyMode);
-        para_wrap(pv_mmu_ops.lazy_mode.leave, vmi_leave_lazy,
+        para_wrap(pv_mmu_ops.lazy_mode.leave, vmi_leave_lazy_mmu,
                   set_lazy_mode, SetLazyMode);
 
         /* user and kernel flush are just handled with different flags to FlushTLB */