KVM: MMU: Coalesce remote tlb flushes

Host side TLB flush can be merged together if multiple
spte need to be write-protected.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 401eb7ce3207..9a57e1a01449 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -513,6 +513,7 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn)
 {
         unsigned long *rmapp;
         u64 *spte;
+        int write_protected = 0;
 
         gfn = unalias_gfn(kvm, gfn);
         rmapp = gfn_to_rmap(kvm, gfn);
@@ -522,11 +523,14 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn)
                 BUG_ON(!spte);
                 BUG_ON(!(*spte & PT_PRESENT_MASK));
                 rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
-                if (is_writeble_pte(*spte))
+                if (is_writeble_pte(*spte)) {
                         set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
-                kvm_flush_remote_tlbs(kvm);
+                        write_protected = 1;
+                }
                 spte = rmap_next(kvm, rmapp, spte);
         }
+        if (write_protected)
+                kvm_flush_remote_tlbs(kvm);
 }
 
 #ifdef MMU_DEBUG