KVM: x86: Defer MMU sync on PCID invalidation

Defer the MMU sync on PCID invalidation so that multiple sync requests in
a single VM-Exit are batched.  This is a very minor optimization as
checking for unsync'd children is quite cheap.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609234235.1244004-13-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 41b9361..9ca30a3 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1074,7 +1074,7 @@ static void kvm_invalidate_pcid(struct kvm_vcpu *vcpu, unsigned long pcid)
         * happen anyway before switching to any other CR3.
         */
        if (kvm_get_active_pcid(vcpu) == pcid) {
-               kvm_mmu_sync_roots(vcpu);
+               kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
                kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
        }