From c972f3b125d8818748429b94cd2e59f473943a33 Mon Sep 17 00:00:00 2001 From: Takuya Yoshikawa Date: Tue, 8 Jan 2013 19:43:28 +0900 Subject: [PATCH] KVM: Write protect the updated slot only when dirty logging is enabled Calling kvm_mmu_slot_remove_write_access() for a deleted slot does nothing but search for non-existent mmu pages which have mappings to that deleted memory; this is safe but a waste of time. Since we want to make the function rmap based in a later patch, in a manner which makes it unsafe to be called for a deleted slot, we makes the caller see if the slot is non-zero and being dirty logged. Reviewed-by: Marcelo Tosatti Signed-off-by: Takuya Yoshikawa Signed-off-by: Gleb Natapov --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 1 - 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1c9c834b72f0..add5e4801968 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6897,7 +6897,13 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, spin_lock(&kvm->mmu_lock); if (nr_mmu_pages) kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages); - kvm_mmu_slot_remove_write_access(kvm, mem->slot); + /* + * Write protect all pages for dirty logging. + * Existing largepage mappings are destroyed here and new ones will + * not be created until the end of the logging. + */ + if (npages && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES)) + kvm_mmu_slot_remove_write_access(kvm, mem->slot); spin_unlock(&kvm->mmu_lock); /* * If memory slot is created, or moved, we need to clear all diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index e45c20ca422a..f689a6d7f9d4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -817,7 +817,6 @@ int __kvm_set_memory_region(struct kvm *kvm, if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) { if (kvm_create_dirty_bitmap(&new) < 0) goto out_free; - /* destroy any largepage mappings for dirty tracking */ } if (!npages || base_gfn != old.base_gfn) { -- 2.11.0