[PATCH 3/5] drm/vmwgfx: Fail to initialize on broken configs

[Zack Rusin <zackr@vmware.com>]

Some of our hosts have a bug where rescaning a pci bus results in stale
fifo memory being mapped on the host. This makes any fifo communication
impossible resulting in various kernel crashes.

Instead of unexpectedly crashing, predictably fail to load the driver
which will preserve the system.

Fixes: fb1d9738ca05 ("drm/vmwgfx: Add DRM driver for VMware Virtual GPU")
Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c b/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
index 67db472d3493..a3bfbb6c3e14 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cmd.c
@@ -145,6 +145,13 @@ struct vmw_fifo_state *vmw_fifo_create(struct vmw_private *dev_priv)
 		 (unsigned int) max,
 		 (unsigned int) min,
 		 (unsigned int) fifo->capabilities);
+
+	if (unlikely(min >= max)) {
+		drm_warn(&dev_priv->drm,
+			 "FIFO memory is not usable. Driver failed to initialize.");
+		return ERR_PTR(-ENXIO);
+	}
+
 	return fifo;
 }
 
-- 
2.30.2