drm/i915/gtt: Disable read-only support under GVT

commit c9e66688 upstream.

GVT is not propagating the PTE bits, and is always setting the
read-write bit, thus breaking read-only support.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180712185315.3288-3-chris@chris-wilson.co.ukSigned-off--by: Jon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -1525,8 +1525,12 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 	ppgtt->base.unbind_vma = ppgtt_unbind_vma;
 	ppgtt->base.bind_vma = ppgtt_bind_vma;
 
-	/* From bdw, there is support for read-only pages in the PPGTT */
-	ppgtt->base.has_read_only = true;
+	/*
+	 * From bdw, there is support for read-only pages in the PPGTT.
+	 *
+	 * XXX GVT is not honouring the lack of RW in the PTE bits.
+	 */
+	ppgtt->base.has_read_only = !intel_vgpu_active(to_i915(ppgtt->base.dev));
 
 	ppgtt->debug_dump = gen8_dump_ppgtt;