KVM: x86: nSVM: support PAUSE filtering when L0 doesn't intercept PAUSE

Expose the pause filtering and threshold in the guest CPUID
and support PAUSE filtering when possible:

- If the L0 doesn't intercept PAUSE (cpu_pm=on), then allow L1 to
  have full control over PAUSE filtering.

- if the L1 doesn't intercept PAUSE, use host values and update
  the adaptive count/threshold even when running nested.

- Otherwise always exit to L1; it is not really possible to merge
  the fields correctly.  It is expected that in this case, userspace
  will not enable this feature in the guest CPUID, to avoid having the
  guest update both fields pointlessly.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220322174050.241850-4-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index f1332d802ec8..fe0011771b10 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -668,6 +668,29 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
 	if (!nested_vmcb_needs_vls_intercept(svm))
 		vmcb02->control.virt_ext |= VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
 
+	if (kvm_pause_in_guest(svm->vcpu.kvm)) {
+		/* use guest values since host doesn't use them */
+		vmcb02->control.pause_filter_count =
+				svm->pause_filter_enabled ?
+				svm->nested.ctl.pause_filter_count : 0;
+
+		vmcb02->control.pause_filter_thresh =
+				svm->pause_threshold_enabled ?
+				svm->nested.ctl.pause_filter_thresh : 0;
+
+	} else if (!vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_PAUSE)) {
+		/* use host values when guest doesn't use them */
+		vmcb02->control.pause_filter_count = vmcb01->control.pause_filter_count;
+		vmcb02->control.pause_filter_thresh = vmcb01->control.pause_filter_thresh;
+	} else {
+		/*
+		 * Intercept every PAUSE otherwise and
+		 * ignore both host and guest values
+		 */
+		vmcb02->control.pause_filter_count = 0;
+		vmcb02->control.pause_filter_thresh = 0;
+	}
+
 	nested_svm_transition_tlb_flush(vcpu);
 
 	/* Enter Guest-Mode */
@@ -928,6 +951,9 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 	vmcb12->control.event_inj         = svm->nested.ctl.event_inj;
 	vmcb12->control.event_inj_err     = svm->nested.ctl.event_inj_err;
 
+	if (!kvm_pause_in_guest(vcpu->kvm) && vmcb02->control.pause_filter_count)
+		vmcb01->control.pause_filter_count = vmcb02->control.pause_filter_count;
+
 	nested_svm_copy_common_state(svm->nested.vmcb02.ptr, svm->vmcb01.ptr);
 
 	svm_switch_vmcb(svm, &svm->vmcb01);