x86: avoid redundant TLB flushes

While in some places the guest requested flushes were already folded
into the deferred ops, this wasn't done consistently.

Also avoid using an uninitialized variable, even if doing so has no
correctness issue.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 55caac0aeb4823c9efd4c2e7e884d04d41f66f12..6fe26a3468e2bdc2fb97d080d6fb884a86b6e26d 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -2773,7 +2773,7 @@ int do_mmuext_op(
         }
 
         case MMUEXT_TLB_FLUSH_ALL:
-            flush_tlb_mask(d->domain_dirty_cpumask);
+            this_cpu(percpu_mm_info).deferred_ops |= DOP_FLUSH_ALL_TLBS;
             break;
     
         case MMUEXT_INVLPG_ALL:
@@ -3567,34 +3567,40 @@ int do_update_va_mapping(unsigned long va, u64 val64,
     if ( pl1e )
         guest_unmap_l1e(v, pl1e);
 
-    process_deferred_ops();
-
     switch ( flags & UVMF_FLUSHTYPE_MASK )
     {
     case UVMF_TLB_FLUSH:
         switch ( (bmap_ptr = flags & ~UVMF_FLUSHTYPE_MASK) )
         {
         case UVMF_LOCAL:
-            flush_tlb_local();
+            this_cpu(percpu_mm_info).deferred_ops |= DOP_FLUSH_TLB;
             break;
         case UVMF_ALL:
-            flush_tlb_mask(d->domain_dirty_cpumask);
+            this_cpu(percpu_mm_info).deferred_ops |= DOP_FLUSH_ALL_TLBS;
             break;
         default:
+            if ( this_cpu(percpu_mm_info).deferred_ops & DOP_FLUSH_ALL_TLBS )
+                break;
             if ( unlikely(!is_pv_32on64_domain(d) ?
                           get_user(vmask, (unsigned long *)bmap_ptr) :
                           get_user(vmask, (unsigned int *)bmap_ptr)) )
-                rc = -EFAULT;
+                rc = -EFAULT, vmask = 0;
             pmask = vcpumask_to_pcpumask(d, vmask);
+            if ( cpu_isset(smp_processor_id(), pmask) )
+                this_cpu(percpu_mm_info).deferred_ops &= ~DOP_FLUSH_TLB;
             flush_tlb_mask(pmask);
             break;
         }
         break;
 
     case UVMF_INVLPG:
+        if ( this_cpu(percpu_mm_info).deferred_ops & DOP_FLUSH_ALL_TLBS )
+            break;
         switch ( (bmap_ptr = flags & ~UVMF_FLUSHTYPE_MASK) )
         {
         case UVMF_LOCAL:
+            if ( this_cpu(percpu_mm_info).deferred_ops & DOP_FLUSH_TLB )
+                break;
             if ( !paging_mode_enabled(d) ||
                  (paging_invlpg(v, va) != 0) ) 
                 flush_tlb_one_local(va);
@@ -3606,14 +3612,18 @@ int do_update_va_mapping(unsigned long va, u64 val64,
             if ( unlikely(!is_pv_32on64_domain(d) ?
                           get_user(vmask, (unsigned long *)bmap_ptr) :
                           get_user(vmask, (unsigned int *)bmap_ptr)) )
-                rc = -EFAULT;
+                rc = -EFAULT, vmask = 0;
             pmask = vcpumask_to_pcpumask(d, vmask);
+            if ( this_cpu(percpu_mm_info).deferred_ops & DOP_FLUSH_TLB )
+                cpu_clear(smp_processor_id(), pmask);
             flush_tlb_one_mask(pmask, va);
             break;
         }
         break;
     }
 
+    process_deferred_ops();
+
     return rc;
 }