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/lguest/boot.c b/arch/x86/lguest/boot.c
index 9fe4ddaa8f6f..41a5562e710e 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -147,10 +147,16 @@ static void lazy_hcall(unsigned long call,
 
 /* When lazy mode is turned off reset the per-cpu lazy mode variable and then
  * issue the do-nothing hypercall to flush any stored calls. */
-static void lguest_leave_lazy_mode(void)
+static void lguest_leave_lazy_mmu_mode(void)
 {
-        paravirt_leave_lazy(paravirt_get_lazy_mode());
         hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+        paravirt_leave_lazy_mmu();
+}
+
+static void lguest_leave_lazy_cpu_mode(void)
+{
+        hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+        paravirt_leave_lazy_cpu();
 }
 
 /*G:033
@@ -1026,7 +1032,7 @@ __init void lguest_init(void)
         pv_cpu_ops.write_idt_entry = lguest_write_idt_entry;
         pv_cpu_ops.wbinvd = lguest_wbinvd;
         pv_cpu_ops.lazy_mode.enter = paravirt_enter_lazy_cpu;
-        pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_mode;
+        pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_cpu_mode;
 
         /* pagetable management */
         pv_mmu_ops.write_cr3 = lguest_write_cr3;
@@ -1039,7 +1045,7 @@ __init void lguest_init(void)
         pv_mmu_ops.read_cr2 = lguest_read_cr2;
         pv_mmu_ops.read_cr3 = lguest_read_cr3;
         pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu;
-        pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mode;
+        pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mmu_mode;
 
 #ifdef CONFIG_X86_LOCAL_APIC
         /* apic read/write intercepts */