drm/vmwgfx: Fix black screen and device errors when running without fbdev

When we are running without fbdev, transitioning from the login screen to
X or gnome-shell/wayland will cause a vt switch and the driver will disable
svga mode, losing all modesetting resources. However, the kms atomic state
does not reflect that and may think that a crtc is still turned on, which
will cause device errors when we try to bind an fb to the crtc, and the
screen will remain black.

Fix this by turning off all kms resources before disabling svga mode.

Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -1337,6 +1337,19 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
  */
 void vmw_svga_disable(struct vmw_private *dev_priv)
 {
+	/*
+	 * Disabling SVGA will turn off device modesetting capabilities, so
+	 * notify KMS about that so that it doesn't cache atomic state that
+	 * isn't valid anymore, for example crtcs turned on.
+	 * Strictly we'd want to do this under the SVGA lock (or an SVGA mutex),
+	 * but vmw_kms_lost_device() takes the reservation sem and thus we'll
+	 * end up with lock order reversal. Thus, a master may actually perform
+	 * a new modeset just after we call vmw_kms_lost_device() and race with
+	 * vmw_svga_disable(), but that should at worst cause atomic KMS state
+	 * to be inconsistent with the device, causing modesetting problems.
+	 *
+	 */
+	vmw_kms_lost_device(dev_priv->dev);
 	ttm_write_lock(&dev_priv->reservation_sem, false);
 	spin_lock(&dev_priv->svga_lock);
 	if (dev_priv->bdev.man[TTM_PL_VRAM].use_type) {