From d91ffee9ec633c6523ef1ea39c36ace578760258 Mon Sep 17 00:00:00 2001 From: Kai Huang Date: Mon, 12 Jan 2015 15:28:54 +0800 Subject: [PATCH] Optimize TLB flush in kvm_mmu_slot_remove_write_access. No TLB flush is needed when there's no valid rmap in memory slot. Signed-off-by: Kai Huang Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0d0fdd6f002c..97898abe8386 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4302,6 +4302,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) struct kvm_memory_slot *memslot; gfn_t last_gfn; int i; + bool flush = false; memslot = id_to_memslot(kvm->memslots, slot); last_gfn = memslot->base_gfn + memslot->npages - 1; @@ -4318,7 +4319,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) for (index = 0; index <= last_index; ++index, ++rmapp) { if (*rmapp) - __rmap_write_protect(kvm, rmapp, false); + flush |= __rmap_write_protect(kvm, rmapp, + false); if (need_resched() || spin_needbreak(&kvm->mmu_lock)) cond_resched_lock(&kvm->mmu_lock); @@ -4345,7 +4347,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) * instead of PT_WRITABLE_MASK, that means it does not depend * on PT_WRITABLE_MASK anymore. */ - kvm_flush_remote_tlbs(kvm); + if (flush) + kvm_flush_remote_tlbs(kvm); } #define BATCH_ZAP_PAGES 10