KVM: x86: remove unnecessary rmap walk of read-only memslots

There's no write access to remove.  An existing memslot cannot be updated
to set or clear KVM_MEM_READONLY, and any mappings established in a newly
created or moved read-only memslot will already be read-only.

Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Message-Id: <1591128450-11977-2-git-send-email-anthony.yznaga@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9e41b51353401ec42d8b1977d4c636a0ec071477..e11e0494f833af9ef62f84e1af33ed89b1ed5dfb 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10142,11 +10142,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 static void kvm_mmu_slot_apply_flags(struct kvm *kvm,
                                     struct kvm_memory_slot *new)
 {
-       /* Still write protect RO slot */
-       if (new->flags & KVM_MEM_READONLY) {
-               kvm_mmu_slot_remove_write_access(kvm, new, PG_LEVEL_4K);
+       /* Nothing to do for RO slots */
+       if (new->flags & KVM_MEM_READONLY)
                return;
-       }
 
        /*
         * Call kvm_x86_ops dirty logging hooks when they are valid.