drm/i915/gvt: Fix pipe A enable as default for vgpu

observed igt drv_module_reload test case failure on 4.15.0
rc2 kernel with panic due to no active pipe available.

the gpu will reset during unload/load and make pipe config reg
lost which can cause kernel panic issue happen.

this patch is to move pipe enabling to emulate_mointor_status_chagne
to handle vgpu reset case as well.

Fixes: 7e605902 ("drm/i915/gvt: enabled pipe A default on creating vgpu")
Signed-off-by: Xiaolin Zhang <xiaolin.zhang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
(cherry picked from commit f5f00e7d)

drivers/gpu/drm/i915/gvt/display.c

@@ -266,6 +266,8 @@ static void emulate_monitor_status_change(struct intel_vgpu *vgpu)
 	/* Clear host CRT status, so guest couldn't detect this host CRT. */
 	if (IS_BROADWELL(dev_priv))
 		vgpu_vreg(vgpu, PCH_ADPA) &= ~ADPA_CRT_HOTPLUG_MONITOR_MASK;
+
+	vgpu_vreg(vgpu, PIPECONF(PIPE_A)) |= PIPECONF_ENABLE;
 }
 
 static void clean_virtual_dp_monitor(struct intel_vgpu *vgpu, int port_num)
@@ -282,7 +284,6 @@ static void clean_virtual_dp_monitor(struct intel_vgpu *vgpu, int port_num)
 static int setup_virtual_dp_monitor(struct intel_vgpu *vgpu, int port_num,
 				    int type, unsigned int resolution)
 {
-	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
 	struct intel_vgpu_port *port = intel_vgpu_port(vgpu, port_num);
 
 	if (WARN_ON(resolution >= GVT_EDID_NUM))
@@ -308,7 +309,7 @@ static int setup_virtual_dp_monitor(struct intel_vgpu *vgpu, int port_num,
 	port->type = type;
 
 	emulate_monitor_status_change(vgpu);
-	vgpu_vreg(vgpu, PIPECONF(PIPE_A)) |= PIPECONF_ENABLE;
+
 	return 0;
 }