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Commit c972f3b1 authored by Takuya Yoshikawa's avatar Takuya Yoshikawa Committed by Gleb Natapov
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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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent aa11e3a8

arch/x86/kvm/x86.c

+7 −1
Original line number Diff line number Diff line
@@ -6897,6 +6897,12 @@ 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);

	/*

	 * 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);

	/*

virt/kvm/kvm_main.c

+0 −1
Original line number Diff line number Diff line
@@ -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) {