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, 2 insertions, 0 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index df9d5f78385e..2f34d643b567 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -94,6 +94,7 @@ struct thread_info {
 #define TIF_FORCED_TF           24      /* true if TF in eflags artificially */
 #define TIF_DEBUGCTLMSR         25      /* uses thread_struct.debugctlmsr */
 #define TIF_DS_AREA_MSR         26      /* uses thread_struct.ds_area_msr */
+#define TIF_LAZY_MMU_UPDATES    27      /* task is updating the mmu lazily */
 
 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
@@ -115,6 +116,7 @@ struct thread_info {
 #define _TIF_FORCED_TF          (1 << TIF_FORCED_TF)
 #define _TIF_DEBUGCTLMSR        (1 << TIF_DEBUGCTLMSR)
 #define _TIF_DS_AREA_MSR        (1 << TIF_DS_AREA_MSR)
+#define _TIF_LAZY_MMU_UPDATES   (1 << TIF_LAZY_MMU_UPDATES)
 
 /* work to do in syscall_trace_enter() */
 #define _TIF_WORK_SYSCALL_ENTRY \