KVM: nSVM: Fix nested guest support for PAUSE filtering.

Currently, the nested guest's PAUSE intercept intentions are not being
honored.  Instead, since the L0 hypervisor's pause_filter_count and
pause_filter_thresh values are still in place, these values are used
instead of those programmed in the VMCB by the L1 hypervisor.

To honor the desired PAUSE intercept support of the L1 hypervisor, the L0
hypervisor must use the PAUSE filtering fields of the L1 hypervisor. This
requires saving and restoring of both the L0 and L1 hypervisor's PAUSE
filtering fields.

Signed-off-by: William Tambe <william.tambe@amd.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/svm.c

@@ -3281,6 +3281,8 @@ static inline void copy_vmcb_control_area(struct vmcb *dst_vmcb, struct vmcb *fr
 	dst->event_inj_err        = from->event_inj_err;
 	dst->nested_cr3           = from->nested_cr3;
 	dst->virt_ext              = from->virt_ext;
+	dst->pause_filter_count   = from->pause_filter_count;
+	dst->pause_filter_thresh  = from->pause_filter_thresh;
 }
 
 static int nested_svm_vmexit(struct vcpu_svm *svm)
@@ -3359,6 +3361,11 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
 	nested_vmcb->control.event_inj         = 0;
 	nested_vmcb->control.event_inj_err     = 0;
 
+	nested_vmcb->control.pause_filter_count =
+		svm->vmcb->control.pause_filter_count;
+	nested_vmcb->control.pause_filter_thresh =
+		svm->vmcb->control.pause_filter_thresh;
+
 	/* We always set V_INTR_MASKING and remember the old value in hflags */
 	if (!(svm->vcpu.arch.hflags & HF_VINTR_MASK))
 		nested_vmcb->control.int_ctl &= ~V_INTR_MASKING_MASK;
@@ -3536,6 +3543,11 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
 	svm->vmcb->control.event_inj = nested_vmcb->control.event_inj;
 	svm->vmcb->control.event_inj_err = nested_vmcb->control.event_inj_err;
 
+	svm->vmcb->control.pause_filter_count =
+		nested_vmcb->control.pause_filter_count;
+	svm->vmcb->control.pause_filter_thresh =
+		nested_vmcb->control.pause_filter_thresh;
+
 	nested_svm_unmap(page);
 
 	/* Enter Guest-Mode */